diff --git a/net/mctp/route.c b/net/mctp/route.c
index e72cdd4ce588..62952ad5cb63 100644
--- a/net/mctp/route.c
+++ b/net/mctp/route.c
@@ -274,8 +274,10 @@ static void mctp_flow_prepare_output(struct sk_buff *skb, struct mctp_dev *dev)
 
 	key = flow->key;
 
-	if (WARN_ON(key->dev && key->dev != dev))
+	if (key->dev) {
+		WARN_ON(key->dev != dev);
 		return;
+	}
 
 	mctp_dev_set_key(dev, key);
 }