diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index 6bbba36c596957cab633b51795294af773d8af61..40cd13eca82e80f6de41e8d273a739d28c9c8e49 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -38,6 +38,7 @@ KBUILD_CFLAGS += -Wno-sign-compare
 KBUILD_CFLAGS += -Wno-type-limits
 KBUILD_CFLAGS += -Wno-shift-negative-value
 
+KBUILD_CPPFLAGS += -Wundef
 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
 
 else