diff --git a/include/crt/_mingw.h b/include/crt/_mingw.h
index 3896fd1e99d..26757379ce6 100644
--- a/include/crt/_mingw.h
+++ b/include/crt/_mingw.h
@@ -135,6 +135,14 @@
 /* TODO: Mark (almost) all CRT functions as __MINGW_NOTHROW.  This will
 allow GCC to optimize away some EH unwind code, at least in DW2 case.  */
 
+#ifndef __MINGW_EXTENSION
+#if defined(__GNUC__) || defined(__GNUG__)
+#define __MINGW_EXTENSION       __extension__
+#else
+#define __MINGW_EXTENSION
+#endif
+#endif
+
 #ifndef __MSVCRT_VERSION__
 /*  High byte is the major version, low byte is the minor. */
 # define __MSVCRT_VERSION__ 0x0700