diff --git a/drivers/isdn/i4l/isdn_ppp.c b/drivers/isdn/i4l/isdn_ppp.c
index a3551dd..aa30b5c 100644
--- a/drivers/isdn/i4l/isdn_ppp.c
+++ b/drivers/isdn/i4l/isdn_ppp.c
@@ -431,6 +431,7 @@
 	return 0;
 }
 
+#ifdef CONFIG_IPPP_FILTER
 static int get_filter(void __user *arg, struct sock_filter **p)
 {
 	struct sock_fprog uprog;
@@ -465,6 +466,7 @@
 	*p = code;
 	return uprog.len;
 }
+#endif /* CONFIG_IPPP_FILTER */
 
 /*
  * ippp device ioctl