diff --git a/lib/libwebsockets.h b/lib/libwebsockets.h
index 0affce07..328c7c27 100644
--- a/lib/libwebsockets.h
+++ b/lib/libwebsockets.h
@@ -311,7 +311,9 @@ LWS_VISIBLE LWS_EXTERN void lwsl_hexdump(void *buf, size_t len);
 
 
 struct lws;
+#ifndef ARRAY_SIZE
 #define ARRAY_SIZE(x) (sizeof(x) / sizeof(x[0]))
+#endif
 
 /* api change list for user code to test against */