diff --git a/lib/csharp/src/Thrift.csproj b/lib/csharp/src/Thrift.csproj
index 195005a..dc0aa6d 100644
--- a/lib/csharp/src/Thrift.csproj
+++ b/lib/csharp/src/Thrift.csproj
@@ -27,7 +27,7 @@
     <OutputType>Library</OutputType>
     <NoStandardLibraries>false</NoStandardLibraries>
     <AssemblyName>Thrift</AssemblyName>
-    <TargetFrameworkVersion>v3.5</TargetFrameworkVersion>
+    <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
     <RootNamespace>Thrift</RootNamespace>
     <FileUpgradeFlags>
@@ -109,6 +109,7 @@
     <Compile Include="TException.cs" />
     <Compile Include="TApplicationException.cs" />
     <Compile Include="TProcessor.cs" />
+    <Compile Include="Transport\TSocketVersionizer.cs" />
     <Compile Include="Transport\TBufferedTransport.cs" />
     <Compile Include="Transport\TFramedTransport.cs" />
     <Compile Include="Transport\THttpClient.cs" />
@@ -147,4 +148,4 @@
   <ProjectExtensions>
     <VisualStudio AllowExistingFolder="true" />
   </ProjectExtensions>
-</Project>
+</Project>
\ No newline at end of file