diff --git a/sys/sys/mutex.h b/sys/sys/mutex.h
index 8010ebbc158..5fe31eb345f 100644
--- a/sys/sys/mutex.h
+++ b/sys/sys/mutex.h
@@ -395,6 +395,7 @@ extern	int debug_mpsafenet;		/* defined in net/netisr.c */
 	if (!debug_mpsafenet)						\
 		mtx_assert(&Giant, MA_OWNED);				\
 } while (0)
+#define	NET_CALLOUT_MPSAFE	(debug_mpsafenet ? CALLOUT_MPSAFE : 0)
 
 #define	UGAR(rval) do {							\
 	int _val = (rval);						\