diff --git a/src/coap_io.c b/src/coap_io.c
index 3d38aa75..6893221a 100644
--- a/src/coap_io.c
+++ b/src/coap_io.c
@@ -95,7 +95,9 @@ coap_mfree_endpoint(coap_endpoint_t *ep) {
 #define CMSG_NXTHDR WSA_CMSG_NXTHDR
 #define CMSG_LEN WSA_CMSG_LEN
 #define CMSG_SPACE WSA_CMSG_SPACE
+#if(_WIN32_WINNT < 0x0603)
 #define cmsghdr _WSACMSGHDR
+#endif /* (_WIN32_WINNT<0x0603) */
 #endif /* (_WIN32_WINNT>=0x0600) */
 #endif /* defined(__MINGW32__) */