diff --git a/sys/sys/event.h b/sys/sys/event.h
--- a/sys/sys/event.h
+++ b/sys/sys/event.h
@@ -317,7 +317,7 @@
 #define KN_KQUEUE	0x40			/* this knote belongs to a kq */
 #define	KN_SCAN		0x100			/* flux set in kqueue_scan() */
 	int			kn_influx;
-	int			kn_sfflags;	/* saved filter flags */
+	unsigned int		kn_sfflags;	/* saved filter flags */
 	int64_t			kn_sdata;	/* saved data field */
 	union {
 		struct		file *p_fp;	/* file data pointer */