diff --git a/drivers/isdn/i4l/isdn_net.c b/drivers/isdn/i4l/isdn_net.c
index 7c5f970..de6be71 100644
--- a/drivers/isdn/i4l/isdn_net.c
+++ b/drivers/isdn/i4l/isdn_net.c
@@ -292,7 +292,9 @@
 	lp->dialstate = 0;
 	dev->rx_netdev[isdn_dc2minor(lp->isdn_device, lp->isdn_channel)] = NULL;
 	dev->st_netdev[isdn_dc2minor(lp->isdn_device, lp->isdn_channel)] = NULL;
-	isdn_free_channel(lp->isdn_device, lp->isdn_channel, ISDN_USAGE_NET);
+	if (lp->isdn_device != -1 && lp->isdn_channel != -1)
+		isdn_free_channel(lp->isdn_device, lp->isdn_channel,
+				  ISDN_USAGE_NET);
 	lp->flags &= ~ISDN_NET_CONNECTED;
 	lp->isdn_device = -1;
 	lp->isdn_channel = -1;