diff --git a/core/css.js b/core/css.js
index 8eca3fe0c..a59640bae 100644
--- a/core/css.js
+++ b/core/css.js
@@ -772,6 +772,12 @@ Blockly.Css.CONTENT = [
   '.blocklyDropDownDiv .goog-menuitem-rtl .goog-menuitem-icon {',
     'float: right;',
     'margin-right: -24px;',
-  '}'
+  '}',
+
+  '.blocklyComputeCanvas {',
+    'position: absolute;',
+    'width: 0;',
+    'height: 0;',
+  '}',
   /* eslint-enable indent */
 ];