diff --git a/compiler/cpp/src/generate/t_csharp_generator.cc b/compiler/cpp/src/generate/t_csharp_generator.cc
index d592a7c..a5c4bd1 100644
--- a/compiler/cpp/src/generate/t_csharp_generator.cc
+++ b/compiler/cpp/src/generate/t_csharp_generator.cc
@@ -1023,7 +1023,8 @@
     indent() << "TMessage msg = iprot.ReadMessageBegin();" << endl;
 
   f_service_ <<
-    indent() << "ProcessFunction fn = processMap_[msg.Name];" << endl <<
+    indent() << "ProcessFunction fn;" << endl <<
+    indent() << "processMap_.TryGetValue(msg.Name, out fn);" << endl <<
     indent() << "if (fn == null) {" << endl <<
     indent() << "  TProtocolUtil.Skip(iprot, TType.Struct);" << endl <<
     indent() << "  iprot.ReadMessageEnd();" << endl <<