-# Add user supplied AFLAGS and CFLAGS as the last assignments
-KBUILD_AFLAGS += $(AFLAGS)
-KBUILD_CFLAGS += $(CFLAGS)
+# Add user supplied CPPFLAGS, AFLAGS and CFLAGS as the last assignments
+KBUILD_CPPFLAGS += $(CPPFLAGS)
+KBUILD_AFLAGS += $(AFLAGS)
+KBUILD_CFLAGS += $(CFLAGS)