diff --git a/.gitignore b/.gitignore
index 3e4e585ce..8bb24a91b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -35,5 +35,7 @@ _ReSharper*/
 *.userprefs
 *.swp
 *.DotSettings
+#Ignore custom generated files
+LibGit2Sharp/Core/UniqueIdentifier.cs
 
 !Lib/NativeBinaries/*/*.pdb
diff --git a/CustomBuildTasks/CustomBuildTasks.csproj b/CustomBuildTasks/CustomBuildTasks.csproj
new file mode 100644
index 000000000..4afb282bc
--- /dev/null
+++ b/CustomBuildTasks/CustomBuildTasks.csproj
@@ -0,0 +1,42 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
+    <ProjectGuid>{B6138573-A4B9-44E7-83C2-8964CAF51EDA}</ProjectGuid>
+    <OutputType>Library</OutputType>
+    <AppDesignerFolder>Properties</AppDesignerFolder>
+    <RootNamespace>CustomBuildTasks</RootNamespace>
+    <AssemblyName>CustomBuildTasks</AssemblyName>
+    <TargetFrameworkVersion>v3.5</TargetFrameworkVersion>
+    <FileAlignment>512</FileAlignment>
+    <TargetFrameworkProfile />
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
+    <DebugSymbols>true</DebugSymbols>
+    <DebugType>full</DebugType>
+    <Optimize>false</Optimize>
+    <OutputPath>bin\Debug\</OutputPath>
+    <DefineConstants>DEBUG;TRACE</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
+    <DebugType>pdbonly</DebugType>
+    <Optimize>true</Optimize>
+    <OutputPath>bin\Release\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <ItemGroup>
+    <Reference Include="System" />
+    <Reference Include="Microsoft.Build.Framework" />
+    <Reference Include="Microsoft.Build.Utilities" />
+  </ItemGroup>
+  <ItemGroup>
+    <Compile Include="GenerateUniqueIdentifierTask.cs" />
+  </ItemGroup>
+  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
+</Project>
diff --git a/CustomBuildTasks/GenerateUniqueIdentifierTask.cs b/CustomBuildTasks/GenerateUniqueIdentifierTask.cs
new file mode 100644
index 000000000..f33c33e8b
--- /dev/null
+++ b/CustomBuildTasks/GenerateUniqueIdentifierTask.cs
@@ -0,0 +1,36 @@
+using System;
+using System.IO;
+using System.Text;
+using Microsoft.Build.Framework;
+using Microsoft.Build.Utilities;
+
+namespace CustomBuildTasks
+{
+    public class GenerateUniqueIdentifierTask : Task
+    {
+        public override bool Execute()
+        {
+            using (FileStream fs = new FileStream(this.OutputFile, FileMode.Create, FileAccess.Write, FileShare.None))
+            using (StreamWriter sw = new StreamWriter(fs, Encoding.UTF8))
+            {
+                sw.WriteLine("using System;");
+                sw.WriteLine();
+                sw.WriteLine("namespace LibGit2Sharp.Core");
+                sw.WriteLine("{");
+                sw.WriteLine("  internal static class UniqueId");
+                sw.WriteLine("  {");
+                sw.WriteLine("    public const String UniqueIdentifier = \"" + Guid.NewGuid().ToString() + "\";");
+                sw.WriteLine("  }");
+                sw.WriteLine("}");
+            }
+
+            return true;
+        }
+
+        public String OutputFile
+        {
+            get;
+            set;
+        }
+    }
+}
diff --git a/Lib/CustomBuildTasks/CustomBuildTasks.dll b/Lib/CustomBuildTasks/CustomBuildTasks.dll
new file mode 100644
index 000000000..3cd023b83
Binary files /dev/null and b/Lib/CustomBuildTasks/CustomBuildTasks.dll differ
diff --git a/LibGit2Sharp/Core/FilePathMarshaler.cs b/LibGit2Sharp/Core/FilePathMarshaler.cs
index ec239f354..97f81fa2e 100644
--- a/LibGit2Sharp/Core/FilePathMarshaler.cs
+++ b/LibGit2Sharp/Core/FilePathMarshaler.cs
@@ -11,6 +11,7 @@ namespace LibGit2Sharp.Core
     ///
     ///   Use this marshaler for return values, for example:
     ///   [return: MarshalAs(UnmanagedType.CustomMarshaler,
+    ///                      MarshalCookie = UniqueId.UniqueIdentifier,
     ///                      MarshalTypeRef = typeof(FilePathNoCleanupMarshaler))]
     /// </summary>
     internal class FilePathNoCleanupMarshaler : FilePathMarshaler
@@ -42,6 +43,7 @@ public override void CleanUpNativeData(IntPtr pNativeData)
     ///   [DllImport(libgit2)]
     ///   internal static extern int git_index_open(out IndexSafeHandle index,
     ///       [MarshalAs(UnmanagedType.CustomMarshaler,
+    ///                  MarshalCookie = UniqueId.UniqueIdentifier,
     ///                  MarshalTypeRef = typeof(FilePathMarshaler))] FilePath indexpath);
     /// </summary>
     internal class FilePathMarshaler : ICustomMarshaler
diff --git a/LibGit2Sharp/Core/NativeMethods.cs b/LibGit2Sharp/Core/NativeMethods.cs
index cd0078a69..b64c72a4d 100644
--- a/LibGit2Sharp/Core/NativeMethods.cs
+++ b/LibGit2Sharp/Core/NativeMethods.cs
@@ -110,13 +110,13 @@ internal static extern void giterr_set_str(
         internal static extern int git_blob_create_fromdisk(
             ref GitOid id,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path);
 
         [DllImport(libgit2)]
         internal static extern int git_blob_create_fromworkdir(
             ref GitOid id,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath relative_path);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath relative_path);
 
         internal delegate int source_callback(
             IntPtr content,
@@ -127,7 +127,7 @@ internal delegate int source_callback(
         internal static extern int git_blob_create_fromchunks(
             ref GitOid oid,
             RepositorySafeHandle repositoryPtr,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath hintpath,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath hintpath,
             source_callback fileCallback,
             IntPtr data);
 
@@ -141,7 +141,7 @@ internal static extern int git_blob_create_fromchunks(
         internal static extern int git_branch_create(
             out ReferenceSafeHandle ref_out,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string branch_name,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string branch_name,
             GitObjectSafeHandle target, // TODO: GitCommitSafeHandle?
             [MarshalAs(UnmanagedType.Bool)] bool force);
 
@@ -165,7 +165,7 @@ internal static extern int git_branch_foreach(
         internal static extern int git_branch_move(
             out ReferenceSafeHandle ref_out,
             ReferenceSafeHandle reference,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string new_branch_name,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string new_branch_name,
             [MarshalAs(UnmanagedType.Bool)] bool force);
 
         [DllImport(libgit2)]
@@ -173,14 +173,14 @@ internal static extern int git_branch_remote_name(
             byte[] remote_name_out,
             UIntPtr buffer_size,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string canonical_branch_name);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string canonical_branch_name);
 
         [DllImport(libgit2)]
         internal static extern int git_branch_upstream_name(
             byte[] tracking_branch_name_out, // NB: This is more properly a StringBuilder, but it's UTF8
             UIntPtr buffer_size,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string referenceName);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string referenceName);
 
         [DllImport(libgit2)]
         internal static extern int git_checkout_tree(
@@ -197,8 +197,8 @@ internal static extern int git_checkout_index(
         [DllImport(libgit2)]
         internal static extern int git_clone(
             out RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string origin_url,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath workdir_path,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string origin_url,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath workdir_path,
             GitCloneOptions opts);
 
         [DllImport(libgit2)]
@@ -211,21 +211,21 @@ internal static extern int git_clone(
         internal static extern int git_commit_create(
             out GitOid id,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string updateRef,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string updateRef,
             SignatureSafeHandle author,
             SignatureSafeHandle committer,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string encoding,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string message,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string encoding,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string message,
             GitObjectSafeHandle tree,
             int parentCount,
             [MarshalAs(UnmanagedType.LPArray)] [In] IntPtr[] parents);
 
         [DllImport(libgit2)]
-        [return : MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
+        [return : MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
         internal static extern string git_commit_message(GitObjectSafeHandle commit);
 
         [DllImport(libgit2)]
-        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
+        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
         internal static extern string git_commit_message_encoding(GitObjectSafeHandle commit);
 
         [DllImport(libgit2)]
@@ -256,12 +256,12 @@ internal static extern int git_commit_create(
         internal static extern int git_config_get_entry(
             out GitConfigEntryHandle entry,
             ConfigurationSafeHandle cfg,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string name);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string name);
 
         [DllImport(libgit2)]
         internal static extern int git_config_add_file_ondisk(
             ConfigurationSafeHandle cfg,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path,
             uint level,
             bool force);
 
@@ -277,41 +277,41 @@ internal static extern int git_config_open_level(
         [DllImport(libgit2)]
         internal static extern int git_config_parse_bool(
             [MarshalAs(UnmanagedType.Bool)] out bool value,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string valueToParse);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string valueToParse);
 
         [DllImport(libgit2)]
         internal static extern int git_config_parse_int32(
             [MarshalAs(UnmanagedType.I4)] out int value,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string valueToParse);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string valueToParse);
 
         [DllImport(libgit2)]
         internal static extern int git_config_parse_int64(
             [MarshalAs(UnmanagedType.I8)] out long value,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string valueToParse);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string valueToParse);
 
         [DllImport(libgit2)]
         internal static extern int git_config_set_bool(
             ConfigurationSafeHandle cfg,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
             [MarshalAs(UnmanagedType.Bool)] bool value);
 
         [DllImport(libgit2)]
         internal static extern int git_config_set_int32(
             ConfigurationSafeHandle cfg,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
             int value);
 
         [DllImport(libgit2)]
         internal static extern int git_config_set_int64(
             ConfigurationSafeHandle cfg,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
             long value);
 
         [DllImport(libgit2)]
         internal static extern int git_config_set_string(
             ConfigurationSafeHandle cfg,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string value);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string value);
 
         internal delegate int config_foreach_callback(
             IntPtr entry,
@@ -338,8 +338,8 @@ internal delegate int git_cred_acquire_cb(
         [DllImport(libgit2)]
         internal static extern int git_cred_userpass_plaintext_new(
             out IntPtr cred,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof (Utf8Marshaler))] string username,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof (Utf8Marshaler))] string password);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof (Utf8Marshaler))] string username,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof (Utf8Marshaler))] string password);
 
         [DllImport(libgit2)]
         internal static extern void git_diff_list_free(IntPtr diff);
@@ -429,7 +429,7 @@ internal static extern int git_diff_foreach(
         [DllImport(libgit2)]
         internal static extern int git_ignore_add_rule(
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof (Utf8Marshaler))] string rules);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof (Utf8Marshaler))] string rules);
 
         [DllImport(libgit2)]
         internal static extern int git_ignore_clear_internal_rules(RepositorySafeHandle repo);
@@ -438,12 +438,12 @@ internal static extern int git_ignore_add_rule(
         internal static extern int git_ignore_path_is_ignored(
             out int ignored,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path);
 
         [DllImport(libgit2)]
         internal static extern int git_index_add_bypath(
             IndexSafeHandle index,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path);
 
         [DllImport(libgit2)]
         internal static extern int git_index_add(
@@ -456,7 +456,7 @@ internal static extern int git_index_conflict_get(
             out IndexEntrySafeHandle ours,
             out IndexEntrySafeHandle theirs,
             IndexSafeHandle index,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path);
 
         [DllImport(libgit2)]
         internal static extern UIntPtr git_index_entrycount(IndexSafeHandle index);
@@ -468,7 +468,7 @@ internal static extern int git_index_conflict_get(
         internal static extern int git_index_find(
             out UIntPtr pos,
             IndexSafeHandle index,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path);
 
         [DllImport(libgit2)]
         internal static extern void git_index_free(IntPtr index);
@@ -479,7 +479,7 @@ internal static extern int git_index_find(
         [DllImport(libgit2)]
         internal static extern IndexEntrySafeHandle git_index_get_bypath(
             IndexSafeHandle index,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path,
             int stage);
 
         [DllImport(libgit2)]
@@ -488,12 +488,12 @@ internal static extern IndexEntrySafeHandle git_index_get_bypath(
         [DllImport(libgit2)]
         internal static extern int git_index_open(
             out IndexSafeHandle index,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath indexpath);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath indexpath);
 
         [DllImport(libgit2)]
         internal static extern int git_index_remove_bypath(
             IndexSafeHandle index,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path);
 
         [DllImport(libgit2)]
         internal static extern int git_index_write(IndexSafeHandle index);
@@ -512,7 +512,7 @@ internal static extern int git_merge_base(
         internal static extern int git_message_prettify(
             byte[] message_out, // NB: This is more properly a StringBuilder, but it's UTF8
             UIntPtr buffer_size,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string message,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string message,
             bool strip_comments);
 
         [DllImport(libgit2)]
@@ -521,16 +521,16 @@ internal static extern int git_note_create(
             RepositorySafeHandle repo,
             SignatureSafeHandle author,
             SignatureSafeHandle committer,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string notes_ref,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string notes_ref,
             ref GitOid oid,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string note,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string note,
             int force);
 
         [DllImport(libgit2)]
         internal static extern void git_note_free(IntPtr note);
 
         [DllImport(libgit2)]
-        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
+        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
         internal static extern string git_note_message(NoteSafeHandle note);
 
         [DllImport(libgit2)]
@@ -540,20 +540,20 @@ internal static extern int git_note_create(
         internal static extern int git_note_read(
             out NoteSafeHandle note,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string notes_ref,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string notes_ref,
             ref GitOid oid);
 
         [DllImport(libgit2)]
         internal static extern int git_note_remove(
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string notes_ref,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string notes_ref,
             SignatureSafeHandle author,
             SignatureSafeHandle committer,
             ref GitOid oid);
 
         [DllImport(libgit2)]
         internal static extern int git_note_default_ref(
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))] out string notes_ref,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))] out string notes_ref,
             RepositorySafeHandle repo);
 
         internal delegate int git_note_foreach_cb(
@@ -564,7 +564,7 @@ internal delegate int git_note_foreach_cb(
         [DllImport(libgit2)]
         internal static extern int git_note_foreach(
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string notes_ref,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string notes_ref,
             git_note_foreach_cb cb,
             IntPtr payload);
 
@@ -604,7 +604,7 @@ internal static extern int git_object_peel(
         [DllImport(libgit2)]
         internal static extern int git_push_add_refspec(
             PushSafeHandle push,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string pushRefSpec);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string pushRefSpec);
 
         [DllImport(libgit2)]
         internal static extern int git_push_finish(PushSafeHandle push);
@@ -633,7 +633,7 @@ internal delegate int push_status_foreach_cb(
         internal static extern int git_reference_create(
             out ReferenceSafeHandle reference,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
             ref GitOid oid,
             [MarshalAs(UnmanagedType.Bool)] bool force);
 
@@ -641,8 +641,8 @@ internal static extern int git_reference_create(
         internal static extern int git_reference_symbolic_create(
             out ReferenceSafeHandle reference,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string target,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string target,
             [MarshalAs(UnmanagedType.Bool)] bool force);
 
         [DllImport(libgit2)]
@@ -655,7 +655,7 @@ internal delegate int ref_glob_callback(
         [DllImport(libgit2)]
         internal static extern int git_reference_foreach_glob(
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string glob,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string glob,
             ref_glob_callback callback,
             IntPtr payload);
 
@@ -664,16 +664,16 @@ internal static extern int git_reference_foreach_glob(
 
         [DllImport(libgit2)]
         internal static extern int git_reference_is_valid_name(
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string refname);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string refname);
 
         [DllImport(libgit2)]
         internal static extern int git_reference_lookup(
             out ReferenceSafeHandle reference,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string name);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string name);
 
         [DllImport(libgit2)]
-        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
+        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
         internal static extern string git_reference_name(ReferenceSafeHandle reference);
 
         [DllImport(libgit2)]
@@ -683,7 +683,7 @@ internal static extern int git_reference_lookup(
         internal static extern int git_reference_rename(
             out ReferenceSafeHandle ref_out,
             ReferenceSafeHandle reference,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string newName,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string newName,
             [MarshalAs(UnmanagedType.Bool)] bool force);
 
         [DllImport(libgit2)]
@@ -696,10 +696,10 @@ internal static extern int git_reference_rename(
         internal static extern int git_reference_symbolic_set_target(
             out ReferenceSafeHandle ref_out,
             ReferenceSafeHandle reference,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string target);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string target);
 
         [DllImport(libgit2)]
-        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
+        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
         internal static extern string git_reference_symbolic_target(ReferenceSafeHandle reference);
 
         [DllImport(libgit2)]
@@ -740,13 +740,13 @@ internal static extern int git_reflog_append(
             ReflogSafeHandle reflog,
             ref GitOid id,
             SignatureSafeHandle committer,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string msg);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string msg);
 
         [DllImport(libgit2)]
         internal static extern int git_reflog_write(ReflogSafeHandle reflog);
 
         [DllImport(libgit2)]
-        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
+        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
         internal static extern string git_reflog_entry_message(SafeHandle entry);
 
         [DllImport(libgit2)]
@@ -754,7 +754,7 @@ internal static extern int git_refspec_rtransform(
             byte[] target,
             UIntPtr outlen,
             GitRefSpecHandle refSpec,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string name);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string name);
 
         [DllImport(libgit2)]
         internal static extern int git_remote_connect(RemoteSafeHandle remote, GitDirection direction);
@@ -763,8 +763,8 @@ internal static extern int git_refspec_rtransform(
         internal static extern int git_remote_create(
             out RemoteSafeHandle remote,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string url);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string url);
 
         [DllImport(libgit2)]
         internal static extern void git_remote_disconnect(RemoteSafeHandle remote);
@@ -783,13 +783,13 @@ internal static extern int git_remote_download(
 
         [DllImport(libgit2)]
         internal static extern int git_remote_is_valid_name(
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string remote_name);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string remote_name);
 
         [DllImport(libgit2)]
         internal static extern int git_remote_load(
             out RemoteSafeHandle remote,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string name);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string name);
 
         internal delegate int git_headlist_cb(ref GitRemoteHead remoteHeadPtr, IntPtr payload);
 
@@ -797,7 +797,7 @@ internal static extern int git_remote_load(
         internal static extern int git_remote_ls(RemoteSafeHandle remote, git_headlist_cb headlist_cb, IntPtr payload);
 
         [DllImport(libgit2)]
-        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
+        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
         internal static extern string git_remote_name(RemoteSafeHandle remote);
 
         [DllImport(libgit2)]
@@ -810,7 +810,7 @@ internal static extern void git_remote_set_cred_acquire_cb(
             IntPtr payload);
 
         [DllImport(libgit2)]
-        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
+        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
         internal static extern string git_remote_url(RemoteSafeHandle remote);
 
         [DllImport(libgit2)]
@@ -824,7 +824,7 @@ internal static extern int git_remote_set_callbacks(
         [DllImport(libgit2)]
         internal static extern int git_remote_add_fetch(
             RemoteSafeHandle remote,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof (Utf8Marshaler))] string refspec);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof (Utf8Marshaler))] string refspec);
 
         internal delegate void remote_progress_callback(IntPtr str, int len, IntPtr data);
 
@@ -843,9 +843,9 @@ internal delegate int remote_update_tips_callback(
         internal static extern int git_repository_discover(
             byte[] repository_path, // NB: This is more properly a StringBuilder, but it's UTF8
             UIntPtr size,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath start_path,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath start_path,
             [MarshalAs(UnmanagedType.Bool)] bool across_fs,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath ceiling_dirs);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath ceiling_dirs);
 
         internal delegate int git_repository_fetchhead_foreach_cb(
             IntPtr remote_name,
@@ -875,7 +875,7 @@ internal static extern int git_repository_fetchhead_foreach(
         [DllImport(libgit2)]
         internal static extern int git_repository_init(
             out RepositorySafeHandle repository,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path,
             [MarshalAs(UnmanagedType.Bool)] bool isBare);
 
         [DllImport(libgit2)]
@@ -909,17 +909,17 @@ internal static extern int git_repository_message(
         [DllImport(libgit2)]
         internal static extern int git_repository_open(
             out RepositorySafeHandle repository,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path);
 
         [DllImport(libgit2)]
         internal static extern int git_repository_open_ext(
             NullRepositorySafeHandle repository,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath path,
             RepositoryOpenFlags flags,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath ceilingDirs);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath ceilingDirs);
 
         [DllImport(libgit2)]
-        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathNoCleanupMarshaler))]
+        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathNoCleanupMarshaler))]
         internal static extern FilePath git_repository_path(RepositorySafeHandle repository);
 
         [DllImport(libgit2)]
@@ -935,7 +935,7 @@ internal static extern void git_repository_set_index(
         [DllImport(libgit2)]
         internal static extern int git_repository_set_workdir(
             RepositorySafeHandle repository,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath workdir,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath workdir,
             bool update_gitlink);
 
         [DllImport(libgit2)]
@@ -943,7 +943,7 @@ internal static extern int git_repository_state(
             RepositorySafeHandle repository);
 
         [DllImport(libgit2)]
-        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathNoCleanupMarshaler))]
+        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathNoCleanupMarshaler))]
         internal static extern FilePath git_repository_workdir(RepositorySafeHandle repository);
 
         [DllImport(libgit2)]
@@ -956,7 +956,7 @@ internal static extern int git_reset(
         internal static extern int git_revparse_single(
             out GitObjectSafeHandle obj,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string spec);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string spec);
 
         [DllImport(libgit2)]
         internal static extern void git_revwalk_free(IntPtr walker);
@@ -985,8 +985,8 @@ internal static extern int git_revparse_single(
         [DllImport(libgit2)]
         internal static extern int git_signature_new(
             out SignatureSafeHandle signature,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string email,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string email,
             long time,
             int offset);
 
@@ -995,7 +995,7 @@ internal static extern int git_stash_save(
             out GitOid id,
             RepositorySafeHandle repo,
             SignatureSafeHandle stasher,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string message,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string message,
             StashOptions flags);
 
         internal delegate int git_stash_cb(
@@ -1017,7 +1017,7 @@ internal static extern int git_stash_foreach(
         internal static extern int git_status_file(
             out FileStatus statusflags,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath filepath);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath filepath);
 
         internal delegate int git_status_cb(
             IntPtr path,
@@ -1031,7 +1031,7 @@ internal delegate int git_status_cb(
         internal static extern int git_submodule_lookup(
             out SubmoduleSafeHandle reference,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string name);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string name);
 
         internal delegate int submodule_callback(
             IntPtr sm,
@@ -1054,12 +1054,12 @@ internal static extern int git_submodule_save(
             SubmoduleSafeHandle submodule);
 
         [DllImport(libgit2)]
-        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
+        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
         internal static extern string git_submodule_path(
             SubmoduleSafeHandle submodule);
 
         [DllImport(libgit2)]
-        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
+        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
         internal static extern string git_submodule_url(
             SubmoduleSafeHandle submodule);
 
@@ -1100,19 +1100,19 @@ internal static extern int git_submodule_status(
         internal static extern int git_tag_annotation_create(
             out GitOid oid,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
             GitObjectSafeHandle target,
             SignatureSafeHandle signature,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string message);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string message);
 
         [DllImport(libgit2)]
         internal static extern int git_tag_create(
             out GitOid oid,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
             GitObjectSafeHandle target,
             SignatureSafeHandle signature,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string message,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string message,
             [MarshalAs(UnmanagedType.Bool)]
             bool force);
 
@@ -1120,7 +1120,7 @@ internal static extern int git_tag_create(
         internal static extern int git_tag_create_lightweight(
             out GitOid oid,
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string name,
             GitObjectSafeHandle target,
             [MarshalAs(UnmanagedType.Bool)]
             bool force);
@@ -1128,14 +1128,14 @@ internal static extern int git_tag_create_lightweight(
         [DllImport(libgit2)]
         internal static extern int git_tag_delete(
             RepositorySafeHandle repo,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string tagName);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string tagName);
 
         [DllImport(libgit2)]
-        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
+        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
         internal static extern string git_tag_message(GitObjectSafeHandle tag);
 
         [DllImport(libgit2)]
-        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
+        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
         internal static extern string git_tag_name(GitObjectSafeHandle tag);
 
         [DllImport(libgit2)]
@@ -1165,7 +1165,7 @@ internal static extern int git_tag_delete(
         internal static extern int git_tree_entry_bypath(
             out TreeEntrySafeHandle_Owned tree,
             GitObjectSafeHandle root,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath treeentry_path);
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath treeentry_path);
 
         [DllImport(libgit2)]
         internal static extern void git_tree_entry_free(IntPtr treeEntry);
@@ -1174,7 +1174,7 @@ internal static extern int git_tree_entry_bypath(
         internal static extern OidSafeHandle git_tree_entry_id(SafeHandle entry);
 
         [DllImport(libgit2)]
-        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
+        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
         internal static extern string git_tree_entry_name(SafeHandle entry);
 
         [DllImport(libgit2)]
@@ -1190,7 +1190,7 @@ internal static extern int git_tree_entry_bypath(
         internal static extern int git_treebuilder_insert(
             IntPtr entry_out,
             TreeBuilderSafeHandle builder,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string treeentry_name,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(Utf8Marshaler))] string treeentry_name,
             ref GitOid id,
             uint attributes);
 
diff --git a/LibGit2Sharp/Core/Utf8Marshaler.cs b/LibGit2Sharp/Core/Utf8Marshaler.cs
index ec78db8fc..79fd2a6c4 100644
--- a/LibGit2Sharp/Core/Utf8Marshaler.cs
+++ b/LibGit2Sharp/Core/Utf8Marshaler.cs
@@ -11,6 +11,7 @@ namespace LibGit2Sharp.Core
     ///
     ///   Use this marshaler for return values, for example:
     ///   [return: MarshalAs(UnmanagedType.CustomMarshaler,
+    ///                      MarshalCookie = UniqueId.UniqueIdentifier,
     ///                      MarshalTypeRef = typeof(Utf8NoCleanupMarshaler))]
     /// </summary>
     internal class Utf8NoCleanupMarshaler : Utf8Marshaler
@@ -42,6 +43,7 @@ public override void CleanUpNativeData(IntPtr pNativeData)
     ///   [DllImport(libgit2)]
     ///   internal static extern int git_tag_delete(RepositorySafeHandle repo,
     ///       [MarshalAs(UnmanagedType.CustomMarshaler,
+    ///                  MarshalCookie = UniqueId.UniqueIdentifier,
     ///                  MarshalTypeRef = typeof(Utf8Marshaler))] String tagName);
     /// </summary>
     internal class Utf8Marshaler : ICustomMarshaler
diff --git a/LibGit2Sharp/LibGit2Sharp.csproj b/LibGit2Sharp/LibGit2Sharp.csproj
index 65a9f90ee..5e1442721 100644
--- a/LibGit2Sharp/LibGit2Sharp.csproj
+++ b/LibGit2Sharp/LibGit2Sharp.csproj
@@ -250,6 +250,7 @@
     <Compile Include="TreeEntryDefinition.cs" />
     <Compile Include="VoidReference.cs" />
     <Compile Include="Core\RawContentStream.cs" />
+    <Compile Include="Core\UniqueIdentifier.cs" />
   </ItemGroup>
   <ItemGroup>
     <CodeAnalysisDictionary Include="CustomDictionary.xml" />
@@ -261,6 +262,7 @@
     <EmbeddedResource Include="libgit2sharp_hash.txt" />
   </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
+  <Import Project="UniqueIdentifier.targets" />
   <PropertyGroup>
     <PreBuildEvent>
     </PreBuildEvent>
diff --git a/LibGit2Sharp/UniqueIdentifier.targets b/LibGit2Sharp/UniqueIdentifier.targets
new file mode 100644
index 000000000..ef65ddf11
--- /dev/null
+++ b/LibGit2Sharp/UniqueIdentifier.targets
@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+
+  <!-- Import the version of CustomBuildTasks.dll that is dropped in the repository. -->
+  <UsingTask TaskName="GenerateUniqueIdentifierTask" AssemblyFile="..\Lib\CustomBuildTasks\CustomBuildTasks.dll" />
+
+  <!-- Set the path of the generated UniqueIdentifier.cs file. -->
+  <PropertyGroup>
+    <UniqueIdentifierPath>Core\UniqueIdentifier.cs</UniqueIdentifierPath>
+    <CoreCompileDependsOn>$(CoreCompileDependsOn);GenerateUniqueIdentifierCs</CoreCompileDependsOn>
+    <CoreCleanDependsOn>$(CoreCleanDependsOn);CleanUniqueIdentifierCs</CoreCleanDependsOn>
+  </PropertyGroup>
+
+  <!-- This target runs if any of the projects or .cs files for the project have changed since the last time
+      the UniqueIdentifier.cs file was generated. -->
+  <Target Name="GenerateUniqueIdentifierCs"
+          Inputs="$(MSBuildThisFileFullPath);$(MSBuildAllProjects);@(Compile)"
+          Outputs="$(UniqueIdentifierPath)">
+    <GenerateUniqueIdentifierTask OutputFile="$(UniqueIdentifierPath)" />
+  </Target>
+
+  <Target Name="CleanUniqueIdentifierCs">
+    <Delete Files="$(UniqueIdentifierPath)" />
+  </Target>
+
+</Project>