diff --git a/core/cxx_stl_setup.mk b/core/cxx_stl_setup.mk
index 7d3ca5c562..123032508f 100644
--- a/core/cxx_stl_setup.mk
+++ b/core/cxx_stl_setup.mk
@@ -55,8 +55,6 @@ endif
 
 my_cxx_ldlibs :=
 ifneq ($(filter $(my_cxx_stl),libc++ libc++_static),)
-    my_cflags += -D_USING_LIBCXX
-
     ifeq ($($(my_prefix)OS),darwin)
         # libc++'s headers are annotated with availability macros that indicate
         # which version of Mac OS was the first to ship with a libc++ feature