diff --git a/src/kiri-mode/cam/prepare.js b/src/kiri-mode/cam/prepare.js
index dcff2dcd..d1a6a0a1 100644
--- a/src/kiri-mode/cam/prepare.js
+++ b/src/kiri-mode/cam/prepare.js
@@ -42,7 +42,7 @@ CAM.prepare = function(widgets, settings, update) {
     });
 
     const output = print.output.filter(level => Array.isArray(level));
-    print.render = render.path(output, (progress, layer) => {
+    return render.path(output, (progress, layer) => {
         update(0.75 + progress * 0.25, "render", layer);
     }, {
         thin: true,
@@ -54,8 +54,6 @@ CAM.prepare = function(widgets, settings, update) {
         action: "milling",
         maxspeed: settings.process.camFastFeed || 6000
     });
-
-    return print.render;
 };
 
 function prepEach(widget, settings, print, firstPoint, update) {
diff --git a/src/kiri-mode/fdm/prepare.js b/src/kiri-mode/fdm/prepare.js
index 903e1014..6885fc48 100644
--- a/src/kiri-mode/fdm/prepare.js
+++ b/src/kiri-mode/fdm/prepare.js
@@ -768,7 +768,7 @@ FDM.prepare = function(widgets, settings, update) {
 
     // render if not explicitly disabled
     if (settings.render !== false) {
-        print.render = render.path(output, (progress, layer) => {
+        return render.path(output, (progress, layer) => {
             update(0.5 + progress * 0.5, "render", layer);
         }, {
             lineWidth: settings.process.sliceLineWidth,
@@ -779,8 +779,6 @@ FDM.prepare = function(widgets, settings, update) {
             fdm: true
         });
     }
-
-    return print.render;
 };
 
 function slicePrintPath(print, slice, startPoint, offset, output, opt = {}) {
diff --git a/src/kiri-mode/laser/driver.js b/src/kiri-mode/laser/driver.js
index 35c1bf39..fe9d4a69 100644
--- a/src/kiri-mode/laser/driver.js
+++ b/src/kiri-mode/laser/driver.js
@@ -366,7 +366,7 @@ function prepare(widgets, settings, update) {
         });
     }
 
-    return print.render = kiri.render.path(output, (progress, layer) => {
+    return kiri.render.path(output, (progress, layer) => {
         update(0.5 + progress * 0.5, "render", layer);
     }, { thin: true, z: 0, action: "cut", moves: process.knifeOn });
 };