diff --git a/blockly_compressed.js b/blockly_compressed.js
index f3fa933d3..75b306794 100644
--- a/blockly_compressed.js
+++ b/blockly_compressed.js
@@ -1079,7 +1079,7 @@ Blockly.ContextMenu.hide=function(){Blockly.WidgetDiv.hideIfOwner(Blockly.Contex
 Blockly.BlockSvg=function(){this.svgGroup_=Blockly.createSvgElement("g",{},null);this.svgPathDark_=Blockly.createSvgElement("path",{"class":"blocklyPathDark",transform:"translate(1, 1)"},this.svgGroup_);this.svgPath_=Blockly.createSvgElement("path",{"class":"blocklyPath"},this.svgGroup_);this.svgPathLight_=Blockly.createSvgElement("path",{"class":"blocklyPathLight"},this.svgGroup_);this.svgPath_.tooltip=this;Blockly.Tooltip.bindMouseEvents(this.svgPath_)};goog.inherits(Blockly.BlockSvg,Blockly.Block);
 Blockly.BlockSvg.prototype.height=0;Blockly.BlockSvg.prototype.width=0;Blockly.BlockSvg.INLINE=-1;
 Blockly.BlockSvg.prototype.initSvg=function(){goog.asserts.assert(this.workspace.rendered,"Workspace is headless.");for(var a=0,b;b=this.inputList[a];a++)b.init();this.mutator&&this.mutator.createIcon();this.updateColour();this.updateMovable();if(!this.workspace.options.readOnly&&!this.eventsInit_){Blockly.bindEvent_(this.getSvgRoot(),"mousedown",this,this.onMouseDown_);var c=this;Blockly.bindEvent_(this.getSvgRoot(),"touchstart",null,function(a){Blockly.longStart_(a,c)})}goog.isFunction(this.onchange)&&
-!this.eventsInit_&&Blockly.bindEvent_(this.workspace.getCanvas(),"blocklyWorkspaceChange",this,this.onchange);this.eventsInit_=!0;this.getSvgRoot().parentNode||this.workspace.getCanvas().appendChild(this.getSvgRoot())};Blockly.BlockSvg.prototype.select=function(){Blockly.selected&&Blockly.selected.unselect();Blockly.selected=this;this.addSelect();Blockly.fireUiEvent(this.workspace.getCanvas(),"blocklySelectChange")};
+!this.eventsInit_&&(this.onchangeWrapper_=Blockly.bindEvent_(this.workspace.getCanvas(),"blocklyWorkspaceChange",this,this.onchange));this.eventsInit_=!0;this.getSvgRoot().parentNode||this.workspace.getCanvas().appendChild(this.getSvgRoot())};Blockly.BlockSvg.prototype.select=function(){Blockly.selected&&Blockly.selected.unselect();Blockly.selected=this;this.addSelect();Blockly.fireUiEvent(this.workspace.getCanvas(),"blocklySelectChange")};
 Blockly.BlockSvg.prototype.unselect=function(){Blockly.selected=null;this.removeSelect();Blockly.fireUiEvent(this.workspace.getCanvas(),"blocklySelectChange")};Blockly.BlockSvg.prototype.mutator=null;Blockly.BlockSvg.prototype.comment=null;Blockly.BlockSvg.prototype.warning=null;Blockly.BlockSvg.prototype.getIcons=function(){var a=[];this.mutator&&a.push(this.mutator);this.comment&&a.push(this.comment);this.warning&&a.push(this.warning);return a};Blockly.BlockSvg.onMouseUpWrapper_=null;
 Blockly.BlockSvg.onMouseMoveWrapper_=null;
 Blockly.BlockSvg.terminateDrag_=function(){Blockly.BlockSvg.onMouseUpWrapper_&&(Blockly.unbindEvent_(Blockly.BlockSvg.onMouseUpWrapper_),Blockly.BlockSvg.onMouseUpWrapper_=null);Blockly.BlockSvg.onMouseMoveWrapper_&&(Blockly.unbindEvent_(Blockly.BlockSvg.onMouseMoveWrapper_),Blockly.BlockSvg.onMouseMoveWrapper_=null);var a=Blockly.selected;if(2==Blockly.dragMode_&&a){var b=a.getRelativeToSurfaceXY();a.moveConnections_(b.x-a.startDragX,b.y-a.startDragY);delete a.draggedBubbles_;a.setDragging_(!1);
@@ -1108,8 +1108,8 @@ Blockly.BlockSvg.TOP_LEFT_CORNER_START_HIGHLIGHT_RTL="m "+Blockly.BlockSvg.DISTA
 Blockly.BlockSvg.TOP_LEFT_CORNER_HIGHLIGHT="A "+(Blockly.BlockSvg.CORNER_RADIUS-.5)+","+(Blockly.BlockSvg.CORNER_RADIUS-.5)+" 0 0,1 "+Blockly.BlockSvg.CORNER_RADIUS+",0.5";Blockly.BlockSvg.INNER_TOP_LEFT_CORNER=Blockly.BlockSvg.NOTCH_PATH_RIGHT+" h -"+(Blockly.BlockSvg.NOTCH_WIDTH-15-Blockly.BlockSvg.CORNER_RADIUS)+" h -0.5 a "+Blockly.BlockSvg.CORNER_RADIUS+","+Blockly.BlockSvg.CORNER_RADIUS+" 0 0,0 -"+Blockly.BlockSvg.CORNER_RADIUS+","+Blockly.BlockSvg.CORNER_RADIUS;
 Blockly.BlockSvg.INNER_BOTTOM_LEFT_CORNER="a "+Blockly.BlockSvg.CORNER_RADIUS+","+Blockly.BlockSvg.CORNER_RADIUS+" 0 0,0 "+Blockly.BlockSvg.CORNER_RADIUS+","+Blockly.BlockSvg.CORNER_RADIUS;Blockly.BlockSvg.INNER_TOP_LEFT_CORNER_HIGHLIGHT_RTL="a "+Blockly.BlockSvg.CORNER_RADIUS+","+Blockly.BlockSvg.CORNER_RADIUS+" 0 0,0 "+(-Blockly.BlockSvg.DISTANCE_45_OUTSIDE-.5)+","+(Blockly.BlockSvg.CORNER_RADIUS-Blockly.BlockSvg.DISTANCE_45_OUTSIDE);
 Blockly.BlockSvg.INNER_BOTTOM_LEFT_CORNER_HIGHLIGHT_RTL="a "+(Blockly.BlockSvg.CORNER_RADIUS+.5)+","+(Blockly.BlockSvg.CORNER_RADIUS+.5)+" 0 0,0 "+(Blockly.BlockSvg.CORNER_RADIUS+.5)+","+(Blockly.BlockSvg.CORNER_RADIUS+.5);Blockly.BlockSvg.INNER_BOTTOM_LEFT_CORNER_HIGHLIGHT_LTR="a "+(Blockly.BlockSvg.CORNER_RADIUS+.5)+","+(Blockly.BlockSvg.CORNER_RADIUS+.5)+" 0 0,0 "+(Blockly.BlockSvg.CORNER_RADIUS-Blockly.BlockSvg.DISTANCE_45_OUTSIDE)+","+(Blockly.BlockSvg.DISTANCE_45_OUTSIDE+.5);
-Blockly.BlockSvg.prototype.dispose=function(a,b,c){Blockly.selected==this&&Blockly.terminateDrag_();Blockly.ContextMenu.currentBlock==this&&Blockly.ContextMenu.hide();this.unplug(a,!1);b&&this.rendered&&this.disposeUiEffect();this.rendered=!1;b=this.getIcons();for(c=0;c<b.length;c++)b[c].dispose();Blockly.BlockSvg.superClass_.dispose.call(this,a);goog.dom.removeNode(this.svgGroup_);this.svgPathDark_=this.svgPathLight_=this.svgPath_=this.svgGroup_=null};
-Blockly.BlockSvg.prototype.disposeUiEffect=function(){this.workspace.playAudio("delete");var a=Blockly.getSvgXY_(this.svgGroup_),b=this.svgGroup_.cloneNode(!0);b.translateX_=a.x;b.translateY_=a.y;b.setAttribute("transform","translate("+b.translateX_+","+b.translateY_+")");this.workspace.options.svg.appendChild(b);b.bBox_=b.getBBox();b.startDate_=new Date;Blockly.BlockSvg.disposeUiStep_(b,this.RTL)};
+Blockly.BlockSvg.prototype.dispose=function(a,b,c){this.onchangeWrapper_&&(Blockly.unbindEvent_(this.onchangeWrapper_),this.onchangeWrapper_=null);Blockly.selected==this&&Blockly.terminateDrag_();Blockly.ContextMenu.currentBlock==this&&Blockly.ContextMenu.hide();this.unplug(a,!1);b&&this.rendered&&this.disposeUiEffect();this.rendered=!1;b=this.getIcons();for(c=0;c<b.length;c++)b[c].dispose();Blockly.BlockSvg.superClass_.dispose.call(this,a);goog.dom.removeNode(this.svgGroup_);this.svgPathDark_=this.svgPathLight_=
+this.svgPath_=this.svgGroup_=null};Blockly.BlockSvg.prototype.disposeUiEffect=function(){this.workspace.playAudio("delete");var a=Blockly.getSvgXY_(this.svgGroup_),b=this.svgGroup_.cloneNode(!0);b.translateX_=a.x;b.translateY_=a.y;b.setAttribute("transform","translate("+b.translateX_+","+b.translateY_+")");this.workspace.options.svg.appendChild(b);b.bBox_=b.getBBox();b.startDate_=new Date;Blockly.BlockSvg.disposeUiStep_(b,this.RTL)};
 Blockly.BlockSvg.disposeUiStep_=function(a,b){var c=(new Date-a.startDate_)/150;1<c?goog.dom.removeNode(a):(a.setAttribute("transform","translate("+(a.translateX_+(b?-1:1)*a.bBox_.width/2*c+", "+(a.translateY_+a.bBox_.height*c))+") scale("+(1-c)+")"),setTimeout(function(){Blockly.BlockSvg.disposeUiStep_(a,b)},10))};
 Blockly.BlockSvg.prototype.connectionUiEffect=function(){this.workspace.playAudio("click");var a=Blockly.getSvgXY_(this.svgGroup_);this.outputConnection?(a.x+=this.RTL?3:-3,a.y+=13):this.previousConnection&&(a.x+=this.RTL?-23:23,a.y+=3);a=Blockly.createSvgElement("circle",{cx:a.x,cy:a.y,r:0,fill:"none",stroke:"#888","stroke-width":10},this.workspace.options.svg);a.startDate_=new Date;Blockly.BlockSvg.connectionUiStep_(a)};
 Blockly.BlockSvg.connectionUiStep_=function(a){var b=(new Date-a.startDate_)/150;1<b?goog.dom.removeNode(a):(a.setAttribute("r",25*b),a.style.opacity=1-b,setTimeout(function(){Blockly.BlockSvg.connectionUiStep_(a)},10))};
diff --git a/blocks/logic.js b/blocks/logic.js
index 42af0fb8f..4aaf560bb 100644
--- a/blocks/logic.js
+++ b/blocks/logic.js
@@ -310,13 +310,9 @@ Blockly.Blocks['logic_compare'] = {
    * @this Blockly.Block
    */
   onchange: function() {
-    if (!this.workspace) {
-      // Block has been deleted.
-      return;
-    }
     var blockA = this.getInputTargetBlock('A');
     var blockB = this.getInputTargetBlock('B');
-    // Kick blocks that existed prior to this change if they don't match.
+    // Disconnect blocks that existed prior to this change if they don't match.
     if (blockA && blockB &&
         !blockA.outputConnection.checkType_(blockB.outputConnection)) {
       // Mismatch between two inputs.  Disconnect previous and bump it away.
@@ -445,14 +441,10 @@ Blockly.Blocks['logic_ternary'] = {
    * @this Blockly.Block
    */
   onchange: function() {
-    if (!this.workspace) {
-      // Block has been deleted.
-      return;
-    }
     var blockA = this.getInputTargetBlock('THEN');
     var blockB = this.getInputTargetBlock('ELSE');
     var parentConnection = this.outputConnection.targetConnection;
-    // Kick blocks that existed prior to this change if they don't match.
+    // Disconnect blocks that existed prior to this change if they don't match.
     if ((blockA || blockB) && parentConnection) {
       for (var i = 0; i < 2; i++) {
         var block = (i == 1) ? blockA : blockB;
diff --git a/blocks/loops.js b/blocks/loops.js
index ede7faeb1..4616ac3bc 100644
--- a/blocks/loops.js
+++ b/blocks/loops.js
@@ -295,12 +295,8 @@ Blockly.Blocks['controls_flow_statements'] = {
    * @this Blockly.Block
    */
   onchange: function() {
-    if (!this.workspace) {
-      // Block has been deleted.
-      return;
-    }
     var legal = false;
-    // Is the block nested in a control statement?
+    // Is the block nested in a loop?
     var block = this;
     do {
       if (block.type == 'controls_repeat' ||
diff --git a/blocks/procedures.js b/blocks/procedures.js
index c8eb009e7..1ab4514ea 100644
--- a/blocks/procedures.js
+++ b/blocks/procedures.js
@@ -733,10 +733,6 @@ Blockly.Blocks['procedures_ifreturn'] = {
    * @this Blockly.Block
    */
   onchange: function() {
-    if (!this.workspace) {
-      // Block has been deleted.
-      return;
-    }
     var legal = false;
     // Is the block nested in a procedure?
     var block = this;
diff --git a/blocks_compressed.js b/blocks_compressed.js
index e5dd59d04..fd20eb984 100644
--- a/blocks_compressed.js
+++ b/blocks_compressed.js
@@ -47,14 +47,14 @@ b++;break;case "controls_if_else":d=this.getInput("ELSE");a.statementConnection_
 Blockly.Blocks.controls_if_elseif={init:function(){this.setColour(Blockly.Blocks.logic.HUE);this.appendDummyInput().appendField(Blockly.Msg.CONTROLS_IF_ELSEIF_TITLE_ELSEIF);this.setPreviousStatement(!0);this.setNextStatement(!0);this.setTooltip(Blockly.Msg.CONTROLS_IF_ELSEIF_TOOLTIP);this.contextMenu=!1}};
 Blockly.Blocks.controls_if_else={init:function(){this.setColour(Blockly.Blocks.logic.HUE);this.appendDummyInput().appendField(Blockly.Msg.CONTROLS_IF_ELSE_TITLE_ELSE);this.setPreviousStatement(!0);this.setTooltip(Blockly.Msg.CONTROLS_IF_ELSE_TOOLTIP);this.contextMenu=!1}};
 Blockly.Blocks.logic_compare={init:function(){var a=this.RTL?[["=","EQ"],["\u2260","NEQ"],[">","LT"],["\u2265","LTE"],["<","GT"],["\u2264","GTE"]]:[["=","EQ"],["\u2260","NEQ"],["<","LT"],["\u2264","LTE"],[">","GT"],["\u2265","GTE"]];this.setHelpUrl(Blockly.Msg.LOGIC_COMPARE_HELPURL);this.setColour(Blockly.Blocks.logic.HUE);this.setOutput(!0,"Boolean");this.appendValueInput("A");this.appendValueInput("B").appendField(new Blockly.FieldDropdown(a),"OP");this.setInputsInline(!0);var b=this;this.setTooltip(function(){var a=
-b.getFieldValue("OP");return{EQ:Blockly.Msg.LOGIC_COMPARE_TOOLTIP_EQ,NEQ:Blockly.Msg.LOGIC_COMPARE_TOOLTIP_NEQ,LT:Blockly.Msg.LOGIC_COMPARE_TOOLTIP_LT,LTE:Blockly.Msg.LOGIC_COMPARE_TOOLTIP_LTE,GT:Blockly.Msg.LOGIC_COMPARE_TOOLTIP_GT,GTE:Blockly.Msg.LOGIC_COMPARE_TOOLTIP_GTE}[a]});this.prevBlocks_=[null,null]},onchange:function(){if(this.workspace){var a=this.getInputTargetBlock("A"),b=this.getInputTargetBlock("B");if(a&&b&&!a.outputConnection.checkType_(b.outputConnection))for(var c=0;c<this.prevBlocks_.length;c++){var d=
-this.prevBlocks_[c];if(d===a||d===b)d.setParent(null),d.bumpNeighbours_()}this.prevBlocks_[0]=a;this.prevBlocks_[1]=b}}};
+b.getFieldValue("OP");return{EQ:Blockly.Msg.LOGIC_COMPARE_TOOLTIP_EQ,NEQ:Blockly.Msg.LOGIC_COMPARE_TOOLTIP_NEQ,LT:Blockly.Msg.LOGIC_COMPARE_TOOLTIP_LT,LTE:Blockly.Msg.LOGIC_COMPARE_TOOLTIP_LTE,GT:Blockly.Msg.LOGIC_COMPARE_TOOLTIP_GT,GTE:Blockly.Msg.LOGIC_COMPARE_TOOLTIP_GTE}[a]});this.prevBlocks_=[null,null]},onchange:function(){var a=this.getInputTargetBlock("A"),b=this.getInputTargetBlock("B");if(a&&b&&!a.outputConnection.checkType_(b.outputConnection))for(var c=0;c<this.prevBlocks_.length;c++){var d=
+this.prevBlocks_[c];if(d===a||d===b)d.setParent(null),d.bumpNeighbours_()}this.prevBlocks_[0]=a;this.prevBlocks_[1]=b}};
 Blockly.Blocks.logic_operation={init:function(){var a=[[Blockly.Msg.LOGIC_OPERATION_AND,"AND"],[Blockly.Msg.LOGIC_OPERATION_OR,"OR"]];this.setHelpUrl(Blockly.Msg.LOGIC_OPERATION_HELPURL);this.setColour(Blockly.Blocks.logic.HUE);this.setOutput(!0,"Boolean");this.appendValueInput("A").setCheck("Boolean");this.appendValueInput("B").setCheck("Boolean").appendField(new Blockly.FieldDropdown(a),"OP");this.setInputsInline(!0);var b=this;this.setTooltip(function(){var a=b.getFieldValue("OP");return{AND:Blockly.Msg.LOGIC_OPERATION_TOOLTIP_AND,
 OR:Blockly.Msg.LOGIC_OPERATION_TOOLTIP_OR}[a]})}};Blockly.Blocks.logic_negate={init:function(){this.jsonInit({message0:Blockly.Msg.LOGIC_NEGATE_TITLE,args0:[{type:"input_value",name:"BOOL",check:"Boolean"}],output:"Boolean",colour:Blockly.Blocks.logic.HUE,tooltip:Blockly.Msg.LOGIC_NEGATE_TOOLTIP,helpUrl:Blockly.Msg.LOGIC_NEGATE_HELPURL})}};
 Blockly.Blocks.logic_boolean={init:function(){var a=[[Blockly.Msg.LOGIC_BOOLEAN_TRUE,"TRUE"],[Blockly.Msg.LOGIC_BOOLEAN_FALSE,"FALSE"]];this.setHelpUrl(Blockly.Msg.LOGIC_BOOLEAN_HELPURL);this.setColour(Blockly.Blocks.logic.HUE);this.setOutput(!0,"Boolean");this.appendDummyInput().appendField(new Blockly.FieldDropdown(a),"BOOL");this.setTooltip(Blockly.Msg.LOGIC_BOOLEAN_TOOLTIP)}};
 Blockly.Blocks.logic_null={init:function(){this.setHelpUrl(Blockly.Msg.LOGIC_NULL_HELPURL);this.setColour(Blockly.Blocks.logic.HUE);this.setOutput(!0);this.appendDummyInput().appendField(Blockly.Msg.LOGIC_NULL);this.setTooltip(Blockly.Msg.LOGIC_NULL_TOOLTIP)}};
-Blockly.Blocks.logic_ternary={init:function(){this.setHelpUrl(Blockly.Msg.LOGIC_TERNARY_HELPURL);this.setColour(Blockly.Blocks.logic.HUE);this.appendValueInput("IF").setCheck("Boolean").appendField(Blockly.Msg.LOGIC_TERNARY_CONDITION);this.appendValueInput("THEN").appendField(Blockly.Msg.LOGIC_TERNARY_IF_TRUE);this.appendValueInput("ELSE").appendField(Blockly.Msg.LOGIC_TERNARY_IF_FALSE);this.setOutput(!0);this.setTooltip(Blockly.Msg.LOGIC_TERNARY_TOOLTIP);this.prevParentConnection_=null},onchange:function(){if(this.workspace){var a=
-this.getInputTargetBlock("THEN"),b=this.getInputTargetBlock("ELSE"),c=this.outputConnection.targetConnection;if((a||b)&&c)for(var d=0;2>d;d++){var e=1==d?a:b;e&&!e.outputConnection.checkType_(c)&&(c===this.prevParentConnection_?(this.setParent(null),c.sourceBlock_.bumpNeighbours_()):(e.setParent(null),e.bumpNeighbours_()))}this.prevParentConnection_=c}}};
+Blockly.Blocks.logic_ternary={init:function(){this.setHelpUrl(Blockly.Msg.LOGIC_TERNARY_HELPURL);this.setColour(Blockly.Blocks.logic.HUE);this.appendValueInput("IF").setCheck("Boolean").appendField(Blockly.Msg.LOGIC_TERNARY_CONDITION);this.appendValueInput("THEN").appendField(Blockly.Msg.LOGIC_TERNARY_IF_TRUE);this.appendValueInput("ELSE").appendField(Blockly.Msg.LOGIC_TERNARY_IF_FALSE);this.setOutput(!0);this.setTooltip(Blockly.Msg.LOGIC_TERNARY_TOOLTIP);this.prevParentConnection_=null},onchange:function(){var a=
+this.getInputTargetBlock("THEN"),b=this.getInputTargetBlock("ELSE"),c=this.outputConnection.targetConnection;if((a||b)&&c)for(var d=0;2>d;d++){var e=1==d?a:b;e&&!e.outputConnection.checkType_(c)&&(c===this.prevParentConnection_?(this.setParent(null),c.sourceBlock_.bumpNeighbours_()):(e.setParent(null),e.bumpNeighbours_()))}this.prevParentConnection_=c}};
 // Copyright 2012 Google Inc.  Apache License 2.0
 Blockly.Blocks.loops={};Blockly.Blocks.loops.HUE=120;Blockly.Blocks.controls_repeat={init:function(){this.jsonInit({message0:Blockly.Msg.CONTROLS_REPEAT_TITLE,args0:[{type:"field_input",name:"TIMES",text:"10"}],previousStatement:null,nextStatement:null,colour:Blockly.Blocks.loops.HUE,tooltip:Blockly.Msg.CONTROLS_REPEAT_TOOLTIP,helpUrl:Blockly.Msg.CONTROLS_REPEAT_HELPURL});this.appendStatementInput("DO").appendField(Blockly.Msg.CONTROLS_REPEAT_INPUT_DO);this.getField("TIMES").setChangeHandler(Blockly.FieldTextInput.nonnegativeIntegerValidator)}};
 Blockly.Blocks.controls_repeat_ext={init:function(){this.jsonInit({message0:Blockly.Msg.CONTROLS_REPEAT_TITLE,args0:[{type:"input_value",name:"TIMES",check:"Number"}],previousStatement:null,nextStatement:null,colour:Blockly.Blocks.loops.HUE,tooltip:Blockly.Msg.CONTROLS_REPEAT_TOOLTIP,helpUrl:Blockly.Msg.CONTROLS_REPEAT_HELPURL});this.appendStatementInput("DO").appendField(Blockly.Msg.CONTROLS_REPEAT_INPUT_DO)}};
@@ -66,7 +66,7 @@ c=goog.dom.createDom("block",null,c);c.setAttribute("type","variables_get");b.ca
 Blockly.Blocks.controls_forEach={init:function(){this.jsonInit({message0:Blockly.Msg.CONTROLS_FOREACH_TITLE,args0:[{type:"field_variable",name:"VAR",variable:null},{type:"input_value",name:"LIST",check:"Array"}],previousStatement:null,nextStatement:null,colour:Blockly.Blocks.loops.HUE,helpUrl:Blockly.Msg.CONTROLS_FOREACH_HELPURL});this.appendStatementInput("DO").appendField(Blockly.Msg.CONTROLS_FOREACH_INPUT_DO);var a=this;this.setTooltip(function(){return Blockly.Msg.CONTROLS_FOREACH_TOOLTIP.replace("%1",
 a.getFieldValue("VAR"))})},getVars:function(){return[this.getFieldValue("VAR")]},renameVar:function(a,b){Blockly.Names.equals(a,this.getFieldValue("VAR"))&&this.setFieldValue(b,"VAR")},customContextMenu:Blockly.Blocks.controls_for.customContextMenu};
 Blockly.Blocks.controls_flow_statements={init:function(){var a=[[Blockly.Msg.CONTROLS_FLOW_STATEMENTS_OPERATOR_BREAK,"BREAK"],[Blockly.Msg.CONTROLS_FLOW_STATEMENTS_OPERATOR_CONTINUE,"CONTINUE"]];this.setHelpUrl(Blockly.Msg.CONTROLS_FLOW_STATEMENTS_HELPURL);this.setColour(Blockly.Blocks.loops.HUE);this.appendDummyInput().appendField(new Blockly.FieldDropdown(a),"FLOW");this.setPreviousStatement(!0);var b=this;this.setTooltip(function(){var a=b.getFieldValue("FLOW");return{BREAK:Blockly.Msg.CONTROLS_FLOW_STATEMENTS_TOOLTIP_BREAK,
-CONTINUE:Blockly.Msg.CONTROLS_FLOW_STATEMENTS_TOOLTIP_CONTINUE}[a]})},onchange:function(){if(this.workspace){var a=!1,b=this;do{if("controls_repeat"==b.type||"controls_repeat_ext"==b.type||"controls_forEach"==b.type||"controls_for"==b.type||"controls_whileUntil"==b.type){a=!0;break}b=b.getSurroundParent()}while(b);a?this.setWarningText(null):this.setWarningText(Blockly.Msg.CONTROLS_FLOW_STATEMENTS_WARNING)}}};
+CONTINUE:Blockly.Msg.CONTROLS_FLOW_STATEMENTS_TOOLTIP_CONTINUE}[a]})},onchange:function(){var a=!1,b=this;do{if("controls_repeat"==b.type||"controls_repeat_ext"==b.type||"controls_forEach"==b.type||"controls_for"==b.type||"controls_whileUntil"==b.type){a=!0;break}b=b.getSurroundParent()}while(b);a?this.setWarningText(null):this.setWarningText(Blockly.Msg.CONTROLS_FLOW_STATEMENTS_WARNING)}};
 // Copyright 2012 Google Inc.  Apache License 2.0
 Blockly.Blocks.math={};Blockly.Blocks.math.HUE=230;Blockly.Blocks.math_number={init:function(){this.setHelpUrl(Blockly.Msg.MATH_NUMBER_HELPURL);this.setColour(Blockly.Blocks.math.HUE);this.appendDummyInput().appendField(new Blockly.FieldTextInput("0",Blockly.FieldTextInput.numberValidator),"NUM");this.setOutput(!0,"Number");this.setTooltip(Blockly.Msg.MATH_NUMBER_TOOLTIP)}};
 Blockly.Blocks.math_arithmetic={init:function(){var a=[[Blockly.Msg.MATH_ADDITION_SYMBOL,"ADD"],[Blockly.Msg.MATH_SUBTRACTION_SYMBOL,"MINUS"],[Blockly.Msg.MATH_MULTIPLICATION_SYMBOL,"MULTIPLY"],[Blockly.Msg.MATH_DIVISION_SYMBOL,"DIVIDE"],[Blockly.Msg.MATH_POWER_SYMBOL,"POWER"]];this.setHelpUrl(Blockly.Msg.MATH_ARITHMETIC_HELPURL);this.setColour(Blockly.Blocks.math.HUE);this.setOutput(!0,"Number");this.appendValueInput("A").setCheck("Number");this.appendValueInput("B").setCheck("Number").appendField(new Blockly.FieldDropdown(a),
@@ -115,8 +115,8 @@ b));if((b=Blockly.Procedures.getDefinition(b,this.workspace))&&b.mutator&&b.muta
 Blockly.Blocks.procedures_callreturn={init:function(){this.setHelpUrl(Blockly.Msg.PROCEDURES_CALLRETURN_HELPURL);this.setColour(Blockly.Blocks.procedures.HUE);this.appendDummyInput("TOPROW").appendField(Blockly.Msg.PROCEDURES_CALLRETURN_CALL).appendField("","NAME");this.setOutput(!0);this.arguments_=[];this.quarkConnections_={};this.quarkArguments_=null},getProcedureCall:Blockly.Blocks.procedures_callnoreturn.getProcedureCall,renameProcedure:Blockly.Blocks.procedures_callnoreturn.renameProcedure,
 setProcedureParameters:Blockly.Blocks.procedures_callnoreturn.setProcedureParameters,renderArgs_:Blockly.Blocks.procedures_callnoreturn.renderArgs_,mutationToDom:Blockly.Blocks.procedures_callnoreturn.mutationToDom,domToMutation:Blockly.Blocks.procedures_callnoreturn.domToMutation,renameVar:Blockly.Blocks.procedures_callnoreturn.renameVar,customContextMenu:Blockly.Blocks.procedures_callnoreturn.customContextMenu};
 Blockly.Blocks.procedures_ifreturn={init:function(){this.setHelpUrl("http://c2.com/cgi/wiki?GuardClause");this.setColour(Blockly.Blocks.procedures.HUE);this.appendValueInput("CONDITION").setCheck("Boolean").appendField(Blockly.Msg.CONTROLS_IF_MSG_IF);this.appendValueInput("VALUE").appendField(Blockly.Msg.PROCEDURES_DEFRETURN_RETURN);this.setInputsInline(!0);this.setPreviousStatement(!0);this.setNextStatement(!0);this.setTooltip(Blockly.Msg.PROCEDURES_IFRETURN_TOOLTIP);this.hasReturnValue_=!0},mutationToDom:function(){var a=
-document.createElement("mutation");a.setAttribute("value",Number(this.hasReturnValue_));return a},domToMutation:function(a){this.hasReturnValue_=1==a.getAttribute("value");this.hasReturnValue_||(this.removeInput("VALUE"),this.appendDummyInput("VALUE").appendField(Blockly.Msg.PROCEDURES_DEFRETURN_RETURN))},onchange:function(){if(this.workspace){var a=!1,b=this;do{if("procedures_defnoreturn"==b.type||"procedures_defreturn"==b.type){a=!0;break}b=b.getSurroundParent()}while(b);a?("procedures_defnoreturn"==
-b.type&&this.hasReturnValue_?(this.removeInput("VALUE"),this.appendDummyInput("VALUE").appendField(Blockly.Msg.PROCEDURES_DEFRETURN_RETURN),this.hasReturnValue_=!1):"procedures_defreturn"!=b.type||this.hasReturnValue_||(this.removeInput("VALUE"),this.appendValueInput("VALUE").appendField(Blockly.Msg.PROCEDURES_DEFRETURN_RETURN),this.hasReturnValue_=!0),this.setWarningText(null)):this.setWarningText(Blockly.Msg.PROCEDURES_IFRETURN_WARNING)}}};
+document.createElement("mutation");a.setAttribute("value",Number(this.hasReturnValue_));return a},domToMutation:function(a){this.hasReturnValue_=1==a.getAttribute("value");this.hasReturnValue_||(this.removeInput("VALUE"),this.appendDummyInput("VALUE").appendField(Blockly.Msg.PROCEDURES_DEFRETURN_RETURN))},onchange:function(){var a=!1,b=this;do{if("procedures_defnoreturn"==b.type||"procedures_defreturn"==b.type){a=!0;break}b=b.getSurroundParent()}while(b);a?("procedures_defnoreturn"==b.type&&this.hasReturnValue_?
+(this.removeInput("VALUE"),this.appendDummyInput("VALUE").appendField(Blockly.Msg.PROCEDURES_DEFRETURN_RETURN),this.hasReturnValue_=!1):"procedures_defreturn"!=b.type||this.hasReturnValue_||(this.removeInput("VALUE"),this.appendValueInput("VALUE").appendField(Blockly.Msg.PROCEDURES_DEFRETURN_RETURN),this.hasReturnValue_=!0),this.setWarningText(null)):this.setWarningText(Blockly.Msg.PROCEDURES_IFRETURN_WARNING)}};
 // Copyright 2012 Google Inc.  Apache License 2.0
 Blockly.Blocks.texts={};Blockly.Blocks.texts.HUE=160;
 Blockly.Blocks.text={init:function(){this.setHelpUrl(Blockly.Msg.TEXT_TEXT_HELPURL);this.setColour(Blockly.Blocks.texts.HUE);this.appendDummyInput().appendField(this.newQuote_(!0)).appendField(new Blockly.FieldTextInput(""),"TEXT").appendField(this.newQuote_(!1));this.setOutput(!0,"String");this.setTooltip(Blockly.Msg.TEXT_TEXT_TOOLTIP)},newQuote_:function(a){return new Blockly.FieldImage(a==this.RTL?"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAwAAAAKCAQAAAAqJXdxAAAAqUlEQVQI1z3KvUpCcRiA8ef9E4JNHhI0aFEacm1o0BsI0Slx8wa8gLauoDnoBhq7DcfWhggONDmJJgqCPA7neJ7p934EOOKOnM8Q7PDElo/4x4lFb2DmuUjcUzS3URnGib9qaPNbuXvBO3sGPHJDRG6fGVdMSeWDP2q99FQdFrz26Gu5Tq7dFMzUvbXy8KXeAj57cOklgA+u1B5AoslLtGIHQMaCVnwDnADZIFIrXsoXrgAAAABJRU5ErkJggg==":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAwAAAAKCAQAAAAqJXdxAAAAn0lEQVQI1z3OMa5BURSF4f/cQhAKjUQhuQmFNwGJEUi0RKN5rU7FHKhpjEH3TEMtkdBSCY1EIv8r7nFX9e29V7EBAOvu7RPjwmWGH/VuF8CyN9/OAdvqIXYLvtRaNjx9mMTDyo+NjAN1HNcl9ZQ5oQMM3dgDUqDo1l8DzvwmtZN7mnD+PkmLa+4mhrxVA9fRowBWmVBhFy5gYEjKMfz9AylsaRRgGzvZAAAAAElFTkSuQmCC",
diff --git a/core/block_svg.js b/core/block_svg.js
index 803e287fb..67754dc0d 100644
--- a/core/block_svg.js
+++ b/core/block_svg.js
@@ -93,8 +93,8 @@ Blockly.BlockSvg.prototype.initSvg = function() {
   }
   // Bind an onchange function, if it exists.
   if (goog.isFunction(this.onchange) && !this.eventsInit_) {
-    Blockly.bindEvent_(this.workspace.getCanvas(), 'blocklyWorkspaceChange',
-        this, this.onchange);
+    this.onchangeWrapper_ = Blockly.bindEvent_(this.workspace.getCanvas(),
+        'blocklyWorkspaceChange', this, this.onchange);
   }
   this.eventsInit_ = true;
 
@@ -986,6 +986,11 @@ Blockly.BlockSvg.INNER_BOTTOM_LEFT_CORNER_HIGHLIGHT_LTR =
  */
 Blockly.BlockSvg.prototype.dispose = function(healStack, animate,
                                               opt_dontRemoveFromWorkspace) {
+  // Terminate onchange event calls.
+  if (this.onchangeWrapper_) {
+    Blockly.unbindEvent_(this.onchangeWrapper_);
+    this.onchangeWrapper_ = null;
+  }
   // If this block is being dragged, unlink the mouse events.
   if (Blockly.selected == this) {
     Blockly.terminateDrag_();