--- /dev/null
+--- a/Makefile.am
++++ b/Makefile.am
+@@ -61,7 +61,7 @@ COMMON_TESTING_PROTOBUF_FLAGS = $(COMMON
+
+ # The generated protobuf files don't compile with -Werror on win32 so we
+ # disable fatal warnings on WIN32.
+-if ! USING_WIN32
++if USING_WIN32
+ if FATAL_WARNINGS
+ COMMON_CXXFLAGS += -Werror
+ COMMON_PROTOBUF_CXXFLAGS += -Werror -Wno-error=unused-parameter \