--- src/sys/kern/kern_fork.c	2007/06/29 21:54:08	1.69
+++ src/sys/kern/kern_fork.c	2007/07/02 17:06:54	1.70
@@ -589,6 +589,7 @@ restart:
 			mycpu->gd_schedclock.periodic;
 	destproc->p_usched->heuristic_forking(origlp, lp);
 	crit_exit();
+	lp->lwp_cpumask &= usched_mastermask;
 
 	td = lwkt_alloc_thread(NULL, LWKT_THREAD_STACK, -1, 0);
 	lp->lwp_thread = td;