diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index f67e702..2c25581 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1907,7 +1907,7 @@
 		if (fnhe->fnhe_daddr == daddr) {
 			if (fnhe->fnhe_pmtu) {
 				unsigned long expires = fnhe->fnhe_expires;
-				unsigned long diff = jiffies - expires;
+				unsigned long diff = expires - jiffies;
 
 				if (time_before(jiffies, expires)) {
 					rt->rt_pmtu = fnhe->fnhe_pmtu;