Index: if.c
===================================================================
RCS file: /cvs/src/sys/net/if.c,v
retrieving revision 1.428
diff -u -p -r1.428 if.c
--- if.c	7 Mar 2016 18:44:00 -0000	1.428
+++ if.c	9 Mar 2016 04:01:01 -0000
@@ -1130,8 +1130,15 @@ int
 if_congested(void)
 {
 	extern int ticks;
+	int diff;
 
-	return (ticks - ifq_congestion <= (hz / 100));
+	diff = ticks - ifq_congestion;
+	if (diff < 0) {
+		ifq_congestion = ticks - hz;
+		return (0);
+	}
+
+	return (diff <= (hz / 100));
 }
 
 #define	equal(a1, a2)	\