diff --git a/core/binary.mk b/core/binary.mk
index 788472db55..6067615010 100644
--- a/core/binary.mk
+++ b/core/binary.mk
@@ -405,6 +405,13 @@ ifneq (,$(my_cpp_std_version))
    my_cpp_std_cppflags := -std=$(my_cpp_std_version)
 endif
 
+# Extra cflags for projects under external/ directory
+ifeq ($(my_clang),true)
+ifeq ($(filter external/%,$(LOCAL_PATH)),)
+    my_cflags += $(CLANG_EXTERNAL_CFLAGS)
+endif
+endif
+
 # arch-specific static libraries go first so that generic ones can depend on them
 my_static_libraries := $(LOCAL_STATIC_LIBRARIES_$($(my_prefix)$(LOCAL_2ND_ARCH_VAR_PREFIX)ARCH)) $(LOCAL_STATIC_LIBRARIES_$(my_32_64_bit_suffix)) $(my_static_libraries)
 my_whole_static_libraries := $(LOCAL_WHOLE_STATIC_LIBRARIES_$($(my_prefix)$(LOCAL_2ND_ARCH_VAR_PREFIX)ARCH)) $(LOCAL_WHOLE_STATIC_LIBRARIES_$(my_32_64_bit_suffix)) $(my_whole_static_libraries)