diff --git a/drivers/isdn/hisax/hfc_sx.c b/drivers/isdn/hisax/hfc_sx.c
index d925f579bc80..4d3b4b2f2612 100644
--- a/drivers/isdn/hisax/hfc_sx.c
+++ b/drivers/isdn/hisax/hfc_sx.c
@@ -1423,7 +1423,7 @@ int setup_hfcsx(struct IsdnCard *card)
 					}
 					card->para[1] = pnp_port_start(pnp_d, 0);
 					card->para[0] = pnp_irq(pnp_d, 0);
-					if (!card->para[0] || !card->para[1]) {
+					if (card->para[0] == -1 || !card->para[1]) {
 						printk(KERN_ERR "HFC PnP:some resources are missing %ld/%lx\n",
 						       card->para[0], card->para[1]);
 						pnp_disable_dev(pnp_d);