isup: Allow to have a different OPC for ISUP messages.
diff --git a/include/mtp_data.h b/include/mtp_data.h
index b144ba5..e00f13a 100644
--- a/include/mtp_data.h
+++ b/include/mtp_data.h
@@ -39,7 +39,7 @@
  */
 struct mtp_link_set {
 	/* routing info.. */
-	int dpc, opc, sccp_opc;
+	int dpc, opc, sccp_opc, isup_opc;
 	int ni;
 	int spare;