diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index a87071d0ebfedcef4c925864e8ca80cdcd7a2c0b..f7664b956efff05df67b78f791377233d52c73e5 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -739,6 +739,7 @@ static void stmmac_adjust_link(struct net_device *dev)
 			default:
 				netif_warn(priv, link, priv->dev,
 					   "broken speed: %d\n", phydev->speed);
+				phydev->speed = SPEED_UNKNOWN;
 				break;
 			}