diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 0c74da8a04732c..5b17bf124a333c 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2757,7 +2757,7 @@ static struct dst_entry *ipv4_blackhole_dst_check(struct dst_entry *dst, u32 coo
 
 static unsigned int ipv4_blackhole_default_mtu(const struct dst_entry *dst)
 {
-	return 0;
+	return dst->dev->mtu;
 }
 
 static void ipv4_rt_blackhole_update_pmtu(struct dst_entry *dst, u32 mtu)
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 8473016bba4a8c..d8fbd18c94671c 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -157,7 +157,7 @@ static struct dst_ops ip6_dst_ops_template = {
 
 static unsigned int ip6_blackhole_default_mtu(const struct dst_entry *dst)
 {
-	return 0;
+	return dst->dev->mtu;
 }
 
 static void ip6_rt_blackhole_update_pmtu(struct dst_entry *dst, u32 mtu)