diff --git a/src/kiri-mode/cam/ops.js b/src/kiri-mode/cam/ops.js
index 49057ed6..eabbe4ab 100644
--- a/src/kiri-mode/cam/ops.js
+++ b/src/kiri-mode/cam/ops.js
@@ -197,12 +197,13 @@ class OpRough extends CamOp {
             let facing = POLY.offset(inset, -step, { count: 999, flat: true });
             if (isIndexed) {
                 ztOff = (stock.z / 2) - zMax;
-            } else if (ztOff === 0) {
-                // compensate for lack of z top offset in this scenario
-                ztOff = zstep;
             }
             let zdiv = ztOff / roughDown;
             let zstep = (zdiv % 1 > 0) ? ztOff / (Math.floor(zdiv) + 1) : roughDown;
+            if (ztOff === 0) {
+                // compensate for lack of z top offset in this scenario
+                ztOff = zstep;
+            }
             let zsteps = Math.round(ztOff / zstep);
             let camFaces = this.camFaces = [];
             let zstart = zMax + ztOff - zstep;