[vty] Forward declare the extra init function the base is calling
diff --git a/openbsc/src/vty_interface.c b/openbsc/src/vty_interface.c
index b5bdbc8..480b658 100644
--- a/openbsc/src/vty_interface.c
+++ b/openbsc/src/vty_interface.c
@@ -1740,6 +1740,8 @@
 	return CMD_SUCCESS;
 }
 
+extern int bsc_vty_init_extra(struct gsm_network *net);
+
 int bsc_vty_init(struct gsm_network *net)
 {
 	gsmnet = net;