diff --git a/src/mode/cam/slice.js b/src/mode/cam/slice.js
index cf0e6ef7..2dd5f31e 100644
--- a/src/mode/cam/slice.js
+++ b/src/mode/cam/slice.js
@@ -175,7 +175,7 @@
 
         // add shadow perimeter to terrain to catch outside moves off part
         let tabpoly = tabs ? tabs.map(tab => tab.poly) : [];
-        let allpoly = POLY.union([...state.shadowTop.tops, ...tabpoly], 0, true);
+        let allpoly = POLY.union([...state.shadowTop.tops, ...tabpoly, ...state.shadowTop.slice.shadow], 0, true);
         let shadowOff = maxToolDiam < 0 ? allpoly :
             POLY.offset(allpoly, [minToolDiam/2,maxToolDiam/2], { count: 2, flat: true });
         state.terrain.forEach(level => level.tops.appendAll(shadowOff));