diff --git a/libcxx.mk b/libcxx.mk
index b6ab7b7..a325865 100644
--- a/libcxx.mk
+++ b/libcxx.mk
@@ -20,6 +20,7 @@
 	external/libcxx/include \
 	$(LOCAL_C_INCLUDES) \
 
+LOCAL_CFLAGS += -D_USING_LIBCXX
 LOCAL_CPPFLAGS += -nostdinc++
 LOCAL_LDFLAGS += -nodefaultlibs
 LOCAL_LDLIBS += -lm -lc