diff --git a/src/Authentication/Authentication.Test/Helpers/GraphSessionTests.cs b/src/Authentication/Authentication.Test/Helpers/GraphSessionTests.cs
index 6f165d9d568..2bb665e8ee8 100644
--- a/src/Authentication/Authentication.Test/Helpers/GraphSessionTests.cs
+++ b/src/Authentication/Authentication.Test/Helpers/GraphSessionTests.cs
@@ -38,14 +38,24 @@ public void ShouldNotOverwriteExistingGraphSession()
             GraphSession.Initialize(() => new GraphSession());
             Guid originalSessionId = GraphSession.Instance._graphSessionId;
 
-            InvalidOperationException exception = Assert.Throws<InvalidOperationException>(() => GraphSession.Initialize(() => new GraphSession()));
+            GraphSession.Initialize(() => new GraphSession());
 
-            Assert.Equal("An instance of GraphSession already exists. Call Initialize(Func<GraphSession>, bool) to overwrite it.", exception.Message);
             Assert.NotNull(GraphSession.Instance);
             Assert.Equal(originalSessionId, GraphSession.Instance._graphSessionId);
 
             // reset static instance.
             GraphSession.Reset();
         }
+
+        [Fact]
+        public void ShouldThrowExceptionWhenSessionIsNotInitialized()
+        {
+            InvalidOperationException exception = Assert.Throws<InvalidOperationException>(() => GraphSession.Instance);
+
+            Assert.Equal(ErrorConstants.Codes.SessionNotInitialized, exception.Message);
+
+            // reset static instance.
+            GraphSession.Reset();
+        }
     }
 }
diff --git a/src/Authentication/Authentication/Common/GraphSession.cs b/src/Authentication/Authentication/Common/GraphSession.cs
index e86d7157f5f..26a77ba2d42 100644
--- a/src/Authentication/Authentication/Common/GraphSession.cs
+++ b/src/Authentication/Authentication/Common/GraphSession.cs
@@ -93,10 +93,6 @@ public static void Initialize(Func<GraphSession> instanceCreator, bool overwrite
                         _instance = instanceCreator();
                         _initialized = true;
                     }
-                    else
-                    {
-                        throw new InvalidOperationException(string.Format(ErrorConstants.Message.InstanceExists, nameof(GraphSession), "Initialize(Func<GraphSession>, bool)"));
-                    }
                 }
                 finally
                 {
diff --git a/src/Authentication/Authentication/ErrorConstants.cs b/src/Authentication/Authentication/ErrorConstants.cs
index 88bf163e50b..50575b97efc 100644
--- a/src/Authentication/Authentication/ErrorConstants.cs
+++ b/src/Authentication/Authentication/ErrorConstants.cs
@@ -19,7 +19,6 @@ internal static class Message
         {
             internal const string InvalidJWT = "Invalid JWT access token.";
             internal const string MissingAuthContext = "Authentication needed, call Connect-Graph.";
-            internal const string InstanceExists = "An instance of {0} already exists. Call {1} to overwrite it.";
             internal const string NullOrEmptyParameter = "Parameter '{0}' cannot be null or empty.";
             internal const string MacKeyChainFailed = "{0} failed with result code {1}.";
         }