diff --git a/src/csharp/buildall.bat b/src/csharp/buildall.bat
index 34ad9233074..68c61ef0396 100644
--- a/src/csharp/buildall.bat
+++ b/src/csharp/buildall.bat
@@ -5,7 +5,7 @@ setlocal
 @call "%VS120COMNTOOLS%\..\..\vc\vcvarsall.bat" x86
 
 @rem Build the C# native extension
-msbuild ..\..\vsprojects\grpc.sln /t:grpc_csharp_ext || goto :error
+msbuild ..\..\vsprojects\grpc.sln /t:grpc_csharp_ext /p:PlatformToolset=v120 || goto :error
 
 msbuild Grpc.sln /p:Configuration=Debug || goto :error
 msbuild Grpc.sln /p:Configuration=Release || goto :error