--- a/drivers/net/ag71xx/ag71xx_mii.c
+++ b/drivers/net/ag71xx/ag71xx_mii.c
@@ -397,7 +397,7 @@
 	ag->mii_bus.read = ag71xx_mdio_read;
 	ag->mii_bus.write = ag71xx_mdio_write;
 	ag->mii_bus.reset = ag71xx_mdio_reset;
-	ag->mii_bus.id = id;
+	snprintf(ag->mii_bus.id, MII_BUS_ID_SIZE, "%x", id);
 	ag->mii_bus.priv = ag;
 	ag->mii_bus.dev = &ag->dev->dev;