--- a/testing/marionette/capture.js
+++ b/testing/marionette/capture.js
@@ -117,17 +117,19 @@ capture.canvas = function (win, left, to
     // Needs https://github.com/w3c/web-platform-tests/issues/4383 fixed.
     // ctx.DRAWWINDOW_DRAW_VIEW;
     // Bug 1009762 - Crash in [@ mozilla::gl::ReadPixelsIntoDataSurface]
     // ctx.DRAWWINDOW_USE_WIDGET_LAYERS;
    }
 
   ctx.scale(scale, scale);
   ctx.drawWindow(win, left, top, width, height, BG_COLOUR, flags);
-  ctx = capture.highlight_(ctx, highlights, top, left);
+  if (highlights.length) {
+    ctx = capture.highlight_(ctx, highlights, top, left);
+  }
 
   return canvas;
 };
 
 capture.highlight_ = function (context, highlights, top = 0, left = 0) {
   if (!highlights) {
     return;
   }