diff --git a/lib/csharp/Makefile.am b/lib/csharp/Makefile.am
index 5ce4276..7cdec05 100644
--- a/lib/csharp/Makefile.am
+++ b/lib/csharp/Makefile.am
@@ -52,6 +52,7 @@
             src/Transport/TBufferedTransport.cs \
             src/Transport/TTransport.cs \
             src/Transport/TSocket.cs \
+            src/Transport/TSocketVersionizer.cs \
             src/Transport/TTransportException.cs \
             src/Transport/TStreamTransport.cs \
             src/Transport/TFramedTransport.cs \
@@ -75,6 +76,10 @@
 MONO_DEFINES=/d:NET_2_0
 endif
 
+if NET_4_5
+MONO_DEFINES=/d:NET_4_5 -sdk:4.5
+endif
+
 all-local: Thrift.dll
 
 Thrift.dll: $(THRIFTCODE)