diff --git a/openbsc/src/nat/bsc_nat_utils.c b/openbsc/src/nat/bsc_nat_utils.c
index d617f2c..0c79fff 100644
--- a/openbsc/src/nat/bsc_nat_utils.c
+++ b/openbsc/src/nat/bsc_nat_utils.c
@@ -192,3 +192,10 @@
 
 	return 0;
 }
+
+/* Filter out CM Service Requests... */
+int bsc_nat_filter_sccp_cr(struct bsc_connection *bsc, struct msgb *msg, struct bsc_nat_parsed *parsed)
+{
+	/* the data we want to look at is optional. We want to have it here... */
+	return 0;
+}