diff --git a/Makefile b/Makefile
index ed081e3eb8008bb3f37dc37a5ff1d5f7c68f947d..87d659d3c8de9784703329dfa48afbf7e74b919f 100644
--- a/Makefile
+++ b/Makefile
@@ -946,7 +946,7 @@ KBUILD_CFLAGS   += $(call cc-option,-Werror=incompatible-pointer-types)
 KBUILD_CFLAGS   += $(call cc-option,-Werror=designated-init)
 
 # change __FILE__ to the relative path from the srctree
-KBUILD_CFLAGS	+= $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
+KBUILD_CPPFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
 
 # ensure -fcf-protection is disabled when using retpoline as it is
 # incompatible with -mindirect-branch=thunk-extern