diff --git a/core/mutator.js b/core/mutator.js
index 19a0fe86b..4bd98392b 100644
--- a/core/mutator.js
+++ b/core/mutator.js
@@ -118,20 +118,32 @@ Blockly.Mutator.prototype.createEditor_ = function() {
     var quarkXml = null;
   }
   var workspaceOptions = {
+    horizontalLayout: false,
     languageTree: quarkXml,
     parentWorkspace: this.block_.workspace,
     pathToMedia: this.block_.workspace.options.pathToMedia,
     RTL: this.block_.RTL,
+    hasCategories: false,
     toolboxPosition: this.block_.RTL ? Blockly.TOOLBOX_AT_RIGHT :
         Blockly.TOOLBOX_AT_LEFT,
-    horizontalLayout: false,
     getMetrics: this.getFlyoutMetrics_.bind(this),
     setMetrics: null
   };
   this.workspace_ = new Blockly.WorkspaceSvg(workspaceOptions);
   this.workspace_.isMutator = true;
+  this.flyout_ = new Blockly.Flyout();
+  this.flyout_.autoClose = false;
+  this.svgDialog_.appendChild(this.flyout_.createDom());
   this.svgDialog_.appendChild(
-      this.workspace_.createDom('blocklyMutatorBackground'));
+    this.workspace_.createDom('blocklyMutatorBackground'));
+
+  //when mutator bubble is clicked, do not close mutator
+  Blockly.bindEvent_(this.svgDialog_, 'mousedown', this.svgDialog_,
+      function(e) {
+        e.preventDefault();
+        e.stopPropagation();
+      });
+
   return this.svgDialog_;
 };
 
@@ -165,7 +177,12 @@ Blockly.Mutator.prototype.updateEditable = function() {
  */
 Blockly.Mutator.prototype.resizeBubble_ = function() {
   var doubleBorderWidth = 2 * Blockly.Bubble.BORDER_WIDTH;
-  var workspaceSize = this.workspace_.getCanvas().getBBox();
+  try {
+    var workspaceSize = this.workspace_.getCanvas().getBBox();
+  } catch (e) {
+    // Firefox has trouble with hidden elements (Bug 528969).
+    return;
+  }
   var width;
   if (this.block_.RTL) {
     width = -workspaceSize.x;
diff --git a/core/mutator.js.rej b/core/mutator.js.rej
deleted file mode 100644
index 68c9f5e4c..000000000
--- a/core/mutator.js.rej
+++ /dev/null
@@ -1,63 +0,0 @@
-***************
-*** 80,86 ****
-        {'class': 'blocklyIconMark',
-         'x': Blockly.Icon.RADIUS,
-         'y': 2 * Blockly.Icon.RADIUS - 4}, this.iconGroup_);
--   this.iconMark_.appendChild(document.createTextNode('\u2605'));
-  };
-  
-  /**
---- 80,87 ----
-        {'class': 'blocklyIconMark',
-         'x': Blockly.Icon.RADIUS,
-         'y': 2 * Blockly.Icon.RADIUS - 4}, this.iconGroup_);
-+   this.iconMark_.appendChild(document.createTextNode('\u2699'));
-+   //this.iconMark_.appendChild(document.createTextNode('\u2605'));
-  };
-  
-  /**
-***************
-*** 122,127 ****
-    this.flyout_.autoClose = false;
-    this.svgDialog_.appendChild(this.flyout_.createDom());
-    this.svgDialog_.appendChild(this.workspace_.createDom());
-    return this.svgDialog_;
-  };
-  
---- 123,136 ----
-    this.flyout_.autoClose = false;
-    this.svgDialog_.appendChild(this.flyout_.createDom());
-    this.svgDialog_.appendChild(this.workspace_.createDom());
-+ 
-+   //when mutator bubble is clicked, do not close mutator
-+   Blockly.bindEvent_(this.svgDialog_, 'mousedown', this.svgDialog_,
-+       function(e) {
-+         e.preventDefault();
-+         e.stopPropagation();
-+       });
-+ 
-    return this.svgDialog_;
-  };
-  
-***************
-*** 147,153 ****
-   */
-  Blockly.Mutator.prototype.resizeBubble_ = function() {
-    var doubleBorderWidth = 2 * Blockly.Bubble.BORDER_WIDTH;
--   var workspaceSize = this.workspace_.getCanvas().getBBox();
-    var flyoutMetrics = this.flyout_.getMetrics_();
-    var width;
-    if (Blockly.RTL) {
---- 156,167 ----
-   */
-  Blockly.Mutator.prototype.resizeBubble_ = function() {
-    var doubleBorderWidth = 2 * Blockly.Bubble.BORDER_WIDTH;
-+   try {
-+     var workspaceSize = this.workspace_.getCanvas().getBBox();
-+   } catch (e) {
-+     // Firefox has trouble with hidden elements (Bug 528969).
-+     return;
-+   }
-    var flyoutMetrics = this.flyout_.getMetrics_();
-    var width;
-    if (Blockly.RTL) {