diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index de42255017d..5876e2e9392 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -2157,14 +2157,18 @@ sigtd(struct proc *p, int sig, bool fast_sigblock)
 	if (curproc == p && !SIGISMEMBER(curthread->td_sigmask, sig) &&
 	    (!fast_sigblock || curthread->td_sigblock_val == 0))
 		return (curthread);
+
+	/* Find a non-stopped thread that does not mask the signal. */
 	signal_td = NULL;
 	FOREACH_THREAD_IN_PROC(p, td) {
 		if (!SIGISMEMBER(td->td_sigmask, sig) && (!fast_sigblock ||
-		    td != curthread || td->td_sigblock_val == 0)) {
+		    td != curthread || td->td_sigblock_val == 0) &&
+		    (td->td_flags & TDF_BOUNDARY) == 0) {
 			signal_td = td;
 			break;
 		}
 	}
+	/* Select random (first) thread if no better match was found. */
 	if (signal_td == NULL)
 		signal_td = FIRST_THREAD_IN_PROC(p);
 	return (signal_td);