diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index 9bc1177..7c9e6e3 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -406,6 +406,9 @@
 				&& phydev->drv->config_init)
 			phydev->drv->config_init(phydev);
 		break;
+
+	default:
+		return -ENOTTY;
 	}
 
 	return 0;