diff --git a/win32/Makefile.sub b/win32/Makefile.sub
--- win32/Makefile.sub
+++ win32/Makefile.sub
@@ -252,8 +252,10 @@
 ARCH_FLAG = $(PROCESSOR_FLAG)
 !endif
 !if !defined(CFLAGS)
 CFLAGS = $(CFLAGS_NO_ARCH) $(ARCH_FLAG)
+!else
+CFLAGS = $(CFLAGS) $(WARNFLAGS)
 !endif
 !if !defined(CXXFLAGS)
 CXXFLAGS = $(CFLAGS)
 !endif