diff --git a/sys/compat/common/tty_43.c b/sys/compat/common/tty_43.c
index 992053059e19..131d349d47ae 100644
--- a/sys/compat/common/tty_43.c
+++ b/sys/compat/common/tty_43.c
@@ -220,10 +220,10 @@ compat_43_ttioctl(struct tty *tp, u_long com, void *data, int flag,
 	case TIOCLBIC:
 	case TIOCLSET: {
 		struct termios term;
-		int argbits, flags;
+		unsigned argbits, flags;
 
 		argbits = *(int *)data;
-		if (argbits < 0)
+		if (argbits != (argbits & 0xffff))
 			return EINVAL;
 
 		mutex_spin_enter(&tty_lock);