diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index a5ec747..80a19fb 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -622,7 +622,7 @@ sig_ffs(sigset_t *set)
 
 	for (i = 0; i < _SIG_WORDS; i++)
 		if (set->__bits[i])
-			return (ffs(set->__bits[i]) + (i * 32));
+			return (fls(set->__bits[i]) + (i * 32));
 	return (0);
 }
diff --git a/sys/sys/signalvar.h b/sys/sys/signalvar.h
index f7fcaa9..73f4998 100644
--- a/sys/sys/signalvar.h
+++ b/sys/sys/signalvar.h
@@ -108,7 +108,13 @@ typedef void __osiginfohandler_t(int, osiginfo_t *, void *);
  * sigset_t manipulation macros.
  */
 #define	SIGADDSET(set, signo)						\
-	((set).__bits[_SIG_WORD(signo)] |= _SIG_BIT(signo))
+	do {													\
+		if ((set).__bits[_SIG_WORD(signo)] == ~0U)	{			\
+			((set).__bits[_SIG_WORD(signo)] = _SIG_BIT(signo));	\
+		} else {													\
+			((set).__bits[_SIG_WORD(signo)] |= _SIG_BIT(signo));	\
+		}															\
+	} while (0)
 
 #define	SIGDELSET(set, signo)						\
 	((set).__bits[_SIG_WORD(signo)] &= ~_SIG_BIT(signo))