diff --git a/net/ethtool/cabletest.c b/net/ethtool/cabletest.c
index 01db8f394869..c6ca1107c470 100644
--- a/net/ethtool/cabletest.c
+++ b/net/ethtool/cabletest.c
@@ -77,6 +77,7 @@ int ethnl_act_cable_test(struct sk_buff *skb, struct genl_info *info)
 				      info->extack);
 	if (IS_ERR_OR_NULL(phydev)) {
 		ret = -EOPNOTSUPP;
+		rtnl_unlock();
 		goto out_dev_put;
 	}