diff --git a/src/slotmap.h b/src/slotmap.h
index 5d3d891..a26de6d 100644
--- a/src/slotmap.h
+++ b/src/slotmap.h
@@ -68,6 +68,8 @@
 	pthread_rwlock_t rwlock;
 };
 
+uint32_t slotmap_get_id(const struct slot_mapping *map);
+
 /* thread-safe lookup of map by client:slot */
 struct slot_mapping *slotmap_by_client(struct slotmaps *maps, const struct client_slot *client);