diff --git a/drivers/isdn/capi/kcapi.c b/drivers/isdn/capi/kcapi.c
index 9f73bc2727c29f8d8fe393b9fbd8faa37af2218a..f55531869313f2422705c79910568982dd476a2e 100644
--- a/drivers/isdn/capi/kcapi.c
+++ b/drivers/isdn/capi/kcapi.c
@@ -821,6 +821,8 @@ static int old_capi_manufacturer(unsigned int cmd, void __user *data)
 				return -EFAULT;
 		}
 		card = get_capi_ctr_by_nr(ldef.contr);
+		if (!card)
+			return -EINVAL;
 		card = capi_ctr_get(card);
 		if (!card)
 			return -ESRCH;