diff --git a/src/Compilers/Core/Portable/InternalUtilities/FailFast.cs b/src/Compilers/Core/Portable/InternalUtilities/FailFast.cs
index ea6d87c5c3513601da137cc8b68ed3533701873f..00ef07a4c43922c704a0b25244b870d812379469 100644
--- a/src/Compilers/Core/Portable/InternalUtilities/FailFast.cs
+++ b/src/Compilers/Core/Portable/InternalUtilities/FailFast.cs
@@ -18,6 +18,15 @@ internal static void OnFatalException(Exception exception)
                 Debugger.Break();
             }
 
+#if !NETFX20
+            // don't fail fast with an aggregate exception that is masking true exception
+            var aggregate = exception as AggregateException;
+            if (aggregate != null && aggregate.InnerExceptions.Count == 1)
+            {
+                exception = aggregate.InnerExceptions[0];
+            }
+#endif
+
             Environment.FailFast(exception.ToString(), exception);
         }
 
diff --git a/src/ExpressionEvaluator/Core/Source/ResultProvider/NetFX20/ResultProvider.NetFX20.csproj b/src/ExpressionEvaluator/Core/Source/ResultProvider/NetFX20/ResultProvider.NetFX20.csproj
index 156d3b470441bca0de57b5375a030c535ef110bc..1d74a2c828c72e439b824cbfd294b8c6ba0fee52 100644
--- a/src/ExpressionEvaluator/Core/Source/ResultProvider/NetFX20/ResultProvider.NetFX20.csproj
+++ b/src/ExpressionEvaluator/Core/Source/ResultProvider/NetFX20/ResultProvider.NetFX20.csproj
@@ -76,8 +76,14 @@
       <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
     </ProjectReference>
   </ItemGroup>
-  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' " />
-  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' " />
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
+    <DefineConstants>TRACE;DEBUG;NETFX20</DefineConstants>
+    <AllowUnsafeBlocks>false</AllowUnsafeBlocks>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
+    <DefineConstants>TRACE;NETFX20</DefineConstants>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+  </PropertyGroup>
   <ItemGroup>
     <Compile Include="..\Portable\Resources.Designer.cs">
       <Link>Resources.Designer.cs</Link>
@@ -102,4 +108,4 @@
   </ItemGroup>
   <Import Project="..\ResultProvider.projitems" Label="Shared" />
   <Import Project="..\..\..\..\..\..\build\Targets\VSL.Imports.targets" />
-</Project>
+</Project>
\ No newline at end of file