diff --git a/shadowsocks-csharp/app.config b/shadowsocks-csharp/app.config
index c96d7c75..2ab7c8bf 100755
--- a/shadowsocks-csharp/app.config
+++ b/shadowsocks-csharp/app.config
@@ -2,7 +2,6 @@
 <configuration>
 <startup>
   <supportedRuntime version="v4.0" />
-  <supportedRuntime version="v2.0.50727" />
 </startup>
   <runtime>
     <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">