diff --git a/lib/libthr/thread/thr_sig.c b/lib/libthr/thread/thr_sig.c
index d2be9947ac12..420d99b402af 100644
--- a/lib/libthr/thread/thr_sig.c
+++ b/lib/libthr/thread/thr_sig.c
@@ -732,8 +732,12 @@ _setcontext(const ucontext_t *ucp)
 {
 	ucontext_t uc;
 
+	if (ucp == NULL)
+		return (EINVAL);
+	if (!SIGISMEMBER(uc.uc_sigmask, SIGCANCEL))
+		return __sys_setcontext(ucp);
 	(void) memcpy(&uc, ucp, sizeof(uc));
-	remove_thr_signals(&uc.uc_sigmask);
+	SIGDELSET(uc.uc_sigmask, SIGCANCEL);
 	return __sys_setcontext(&uc);
 }
 
@@ -743,7 +747,13 @@ _swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
 {
 	ucontext_t uc;
 
-	(void) memcpy(&uc, ucp, sizeof(uc));
-	remove_thr_signals(&uc.uc_sigmask);
-	return __sys_swapcontext(oucp, &uc);
+	if (oucp == NULL || ucp == NULL)
+		return (EINVAL);
+	if (SIGISMEMBER(ucp->uc_sigmask, SIGCANCEL)) {
+	 	stdout_debug("remove SIGCANCEL\n");	
+		(void) memcpy(&uc, ucp, sizeof(uc));
+		SIGDELSET(uc.uc_sigmask, SIGCANCEL);
+		ucp = &uc;
+	}
+	return __sys_swapcontext(oucp, ucp);
 }