diff --git a/drivers/net/ethernet/3com/3c509.c b/drivers/net/ethernet/3com/3c509.c
index fb68339e1511..67b9a3f4de5e 100644
--- a/drivers/net/ethernet/3com/3c509.c
+++ b/drivers/net/ethernet/3com/3c509.c
@@ -1099,6 +1099,7 @@ el3_netdev_set_ecmd(struct net_device *dev,
 		dev->if_port = 0;
 		break;
 	case PORT_AUI:
+		tmp &= ~(3<<14);
 		tmp |= (1<<14);
 		dev->if_port = 1;
 		break;