diff --git a/openbsc/src/libmsc/vty_interface_layer3.c b/openbsc/src/libmsc/vty_interface_layer3.c
index edece51..4f412b1 100644
--- a/openbsc/src/libmsc/vty_interface_layer3.c
+++ b/openbsc/src/libmsc/vty_interface_layer3.c
@@ -601,7 +601,7 @@
 		return CMD_WARNING;
 	}
 
-	strncpy(subscr->extension, ext, sizeof(subscr->extension));
+	osmo_strlcpy(subscr->extension, ext, sizeof(subscr->extension));
 	db_sync_subscriber(subscr);
 
 	subscr_put(subscr);