diff --git a/src/mscorlib/System.Private.CoreLib.csproj b/src/mscorlib/System.Private.CoreLib.csproj
index 6285e4a3174d..c14ce422fbae 100644
--- a/src/mscorlib/System.Private.CoreLib.csproj
+++ b/src/mscorlib/System.Private.CoreLib.csproj
@@ -29,7 +29,6 @@
     <UTF8OutPut>true</UTF8OutPut>
     <HighEntropyVA>true</HighEntropyVA>
     <ErrorReport>prompt</ErrorReport>
-    <Optimize Condition="'$(Optimize)' == ''">true</Optimize>
     <CLSCompliant>true</CLSCompliant>
     <WarningLevel>4</WarningLevel>
     <TreatWarningsAsErrors>false</TreatWarningsAsErrors>
@@ -76,12 +75,15 @@
   <!-- Configuration specific properties -->
   <PropertyGroup Condition="'$(Configuration)' == 'Debug' or '$(Configuration)' == 'Checked'">
     <DebugSymbols>true</DebugSymbols>
+    <Optimize Condition="'$(Optimize)' == '' and '$(Configuration)' == 'Debug'">false</Optimize>
+    <Optimize Condition="'$(Optimize)' == '' and '$(Configuration)' == 'Checked'">true</Optimize>
     <DebugType>full</DebugType>
     <DefineConstants>DBG;_DEBUG;_LOGGING;DEBUG;TRACE;$(DefineConstants)</DefineConstants>
     <DefineConstants Condition="'$(Platform)' == 'x86' or '$(Platform)' == 'amd64'">CODE_ANALYSIS;$(DefineConstants)</DefineConstants>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)' == 'Release'">
     <DebugSymbols>true</DebugSymbols>
+    <Optimize Condition="'$(Optimize)' == ''">true</Optimize>
     <DebugType>pdbOnly</DebugType>
     <DefineConstants>TRACE;$(DefineConstants)</DefineConstants>
   </PropertyGroup>