Stub out unary call wrapper
diff --git a/src/compiler/cpp_generator.cc b/src/compiler/cpp_generator.cc
index 908b38f..bced4df 100644
--- a/src/compiler/cpp_generator.cc
+++ b/src/compiler/cpp_generator.cc
@@ -146,6 +146,7 @@
 
 std::string GetSourceIncludes() {
   return "#include <grpc++/channel_interface.h>\n"
+         "#include <grpc++/impl/client_unary_call.h>\n"
          "#include <grpc++/impl/rpc_method.h>\n"
          "#include <grpc++/impl/rpc_service_method.h>\n"
          "#include <grpc++/impl/service_type.h>\n"