diff --git a/mk/subdir.mk b/mk/subdir.mk
index d280c309ecf..83b2a8ecf1e 100644
--- a/mk/subdir.mk
+++ b/mk/subdir.mk
@@ -140,6 +140,7 @@ endif
 
 include $1/sub.mk
 sub-subdirs := $$(addprefix $1/,$$(subdirs-y)) $$(subdirs_ext-y)
+cppflags$(sm) := $$(cppflags$(sm)) $$(global-cppflags-y)
 incdirs$(sm) := $(incdirs$(sm)) $$(addprefix $1/,$$(global-incdirs-y))
 thissubdir-incdirs := $(out-dir)/$(base-prefix)$1 $$(addprefix $1/,$$(incdirs-y)) $$(incdirs_ext-y)
 ifneq ($$(libname),)
@@ -168,6 +169,7 @@ aflags-remove-y :=
 subdirs-y :=
 subdirs_ext-y :=
 global-incdirs-y :=
+global-cppflags-y :=
 incdirs-lib-y :=
 incdirs-y :=
 incdirs_ext-y :=