diff --git a/src/signal/sigaltstack.c b/src/signal/sigaltstack.c
index 62cb81adfe16ea1a112448f1654d55a859718374..cfa3f5c19d0de03384ff3f1a3b884149626db07b 100644
--- a/src/signal/sigaltstack.c
+++ b/src/signal/sigaltstack.c
@@ -9,7 +9,7 @@ int sigaltstack(const stack_t *restrict ss, stack_t *restrict old)
 			errno = ENOMEM;
 			return -1;
 		}
-		if (ss->ss_flags & ~SS_DISABLE) {
+		if (ss->ss_flags & SS_ONSTACK) {
 			errno = EINVAL;
 			return -1;
 		}