--- kern_timeout.c.orig	Tue Aug  2 18:23:58 2005
+++ kern_timeout.c	Tue Aug  2 18:24:20 2005
@@ -311,7 +311,7 @@
 					lastfunc = c_func;
 				}
 #endif
-				if ((c_flags & CALLOUT_RETURNUNLOCKED) == 0)
+				if (c_mtx != NULL && ((c_flags & CALLOUT_RETURNUNLOCKED) == 0))
 					mtx_unlock(c_mtx);
 				mtx_lock_spin(&callout_lock);
 done_locked: