diff --git a/src/kiri-mode/cam/ops.js b/src/kiri-mode/cam/ops.js
index 97cc7595..60f39232 100644
--- a/src/kiri-mode/cam/ops.js
+++ b/src/kiri-mode/cam/ops.js
@@ -7,6 +7,7 @@
 // dep: geo.point
 // dep: geo.polygons
 // dep: kiri.slice
+// use: kiri-mode.cam.topo
 gapp.register("kiri-mode.cam.ops", [], (root, exports) => {
 
 const { base, kiri } = root;