diff --git a/blockly_uncompressed.js b/blockly_uncompressed.js
index dc06f2b86..f0a828915 100644
--- a/blockly_uncompressed.js
+++ b/blockly_uncompressed.js
@@ -116,11 +116,11 @@ goog.addDependency("../../core/renderers/minimalist/info.js", ['Blockly.minimali
 goog.addDependency("../../core/renderers/minimalist/renderer.js", ['Blockly.minimalist.Renderer'], ['Blockly.blockRendering', 'Blockly.blockRendering.Renderer', 'Blockly.utils.object', 'Blockly.minimalist.ConstantProvider', 'Blockly.minimalist.Drawer', 'Blockly.minimalist.RenderInfo']);
 goog.addDependency("../../core/renderers/thrasos/info.js", ['Blockly.thrasos', 'Blockly.thrasos.RenderInfo'], ['Blockly.blockRendering.BottomRow', 'Blockly.blockRendering.ExternalValueInput', 'Blockly.blockRendering.InlineInput', 'Blockly.blockRendering.InputRow', 'Blockly.blockRendering.Measurable', 'Blockly.blockRendering.NextConnection', 'Blockly.blockRendering.OutputConnection', 'Blockly.blockRendering.PreviousConnection', 'Blockly.blockRendering.RenderInfo', 'Blockly.blockRendering.Row', 'Blockly.blockRendering.SpacerRow', 'Blockly.blockRendering.StatementInput', 'Blockly.blockRendering.TopRow', 'Blockly.blockRendering.Types', 'Blockly.utils.object']);
 goog.addDependency("../../core/renderers/thrasos/renderer.js", ['Blockly.thrasos.Renderer'], ['Blockly.blockRendering', 'Blockly.blockRendering.Renderer', 'Blockly.thrasos.RenderInfo', 'Blockly.utils.object']);
-goog.addDependency("../../core/renderers/zelos/constants.js", ['Blockly.zelos.ConstantProvider'], ['Blockly.blockRendering.ConstantProvider', 'Blockly.utils.object', 'Blockly.utils.svgPaths']);
+goog.addDependency("../../core/renderers/zelos/constants.js", ['Blockly.zelos.ConstantProvider'], ['Blockly.blockRendering.ConstantProvider', 'Blockly.utils.dom', 'Blockly.utils.object', 'Blockly.utils.svgPaths']);
 goog.addDependency("../../core/renderers/zelos/drawer.js", ['Blockly.zelos.Drawer'], ['Blockly.blockRendering.ConstantProvider', 'Blockly.blockRendering.Drawer', 'Blockly.blockRendering.Types', 'Blockly.utils.object', 'Blockly.zelos.RenderInfo']);
 goog.addDependency("../../core/renderers/zelos/info.js", ['Blockly.zelos', 'Blockly.zelos.RenderInfo'], ['Blockly.blockRendering.BottomRow', 'Blockly.blockRendering.ExternalValueInput', 'Blockly.blockRendering.InlineInput', 'Blockly.blockRendering.InputRow', 'Blockly.blockRendering.Measurable', 'Blockly.blockRendering.NextConnection', 'Blockly.blockRendering.OutputConnection', 'Blockly.blockRendering.PreviousConnection', 'Blockly.blockRendering.RenderInfo', 'Blockly.blockRendering.RoundCorner', 'Blockly.blockRendering.Row', 'Blockly.blockRendering.SquareCorner', 'Blockly.blockRendering.SpacerRow', 'Blockly.blockRendering.StatementInput', 'Blockly.blockRendering.TopRow', 'Blockly.blockRendering.Types', 'Blockly.utils.object', 'Blockly.zelos.AfterStatementSpacerRow', 'Blockly.zelos.BeforeStatementSpacerRow', 'Blockly.zelos.BottomRow', 'Blockly.zelos.TopRow']);
 goog.addDependency("../../core/renderers/zelos/measurables/rows.js", ['Blockly.zelos.BottomRow', 'Blockly.zelos.TopRow', 'Blockly.zelos.AfterStatementSpacerRow', 'Blockly.zelos.BeforeStatementSpacerRow'], ['Blockly.blockRendering.BottomRow', 'Blockly.blockRendering.TopRow', 'Blockly.blockRendering.SpacerRow', 'Blockly.utils.object']);
-goog.addDependency("../../core/renderers/zelos/path_object.js", ['Blockly.zelos.PathObject'], ['Blockly.blockRendering.PathObject', 'Blockly.zelos.ConstantProvider', 'Blockly.utils.object']);
+goog.addDependency("../../core/renderers/zelos/path_object.js", ['Blockly.zelos.PathObject'], ['Blockly.blockRendering.PathObject', 'Blockly.zelos.ConstantProvider', 'Blockly.utils.dom', 'Blockly.utils.object']);
 goog.addDependency("../../core/renderers/zelos/renderer.js", ['Blockly.zelos.Renderer'], ['Blockly.blockRendering', 'Blockly.blockRendering.Renderer', 'Blockly.utils.object', 'Blockly.zelos.ConstantProvider', 'Blockly.zelos.Drawer', 'Blockly.zelos.PathObject', 'Blockly.zelos.RenderInfo']);
 goog.addDependency("../../core/requires.js", ['Blockly.requires'], ['Blockly', 'Blockly.Comment', 'Blockly.HorizontalFlyout', 'Blockly.VerticalFlyout', 'Blockly.FlyoutButton', 'Blockly.Generator', 'Blockly.Toolbox', 'Blockly.Trashcan', 'Blockly.VariablesDynamic', 'Blockly.ZoomControls', 'Blockly.Mutator', 'Blockly.Warning', 'Blockly.FieldAngle', 'Blockly.FieldCheckbox', 'Blockly.FieldColour', 'Blockly.FieldDropdown', 'Blockly.FieldLabelSerializable', 'Blockly.FieldImage', 'Blockly.FieldTextInput', 'Blockly.FieldMultilineInput', 'Blockly.FieldNumber', 'Blockly.FieldVariable', 'Blockly.geras.Renderer', 'Blockly.thrasos.Renderer', 'Blockly.zelos.Renderer', 'Blockly.Themes.Classic', 'Blockly.Themes.Dark', 'Blockly.Themes.Deuteranopia', 'Blockly.Themes.HighContrast', 'Blockly.Themes.Tritanopia']);
 goog.addDependency("../../core/scrollbar.js", ['Blockly.Scrollbar', 'Blockly.ScrollbarPair'], ['Blockly.Touch', 'Blockly.utils', 'Blockly.utils.Coordinate', 'Blockly.utils.dom']);
diff --git a/core/css.js b/core/css.js
index a59640bae..761ac9e39 100644
--- a/core/css.js
+++ b/core/css.js
@@ -254,11 +254,6 @@ Blockly.Css.CONTENT = [
     'stroke-width: 1;',
   '}',
 
-  '.blocklySelected>.blocklyPath {',
-    'stroke: #fc3;',
-    'stroke-width: 3px;',
-  '}',
-
   '.blocklySelected>.blocklyPathLight {',
     'display: none;',
   '}',
diff --git a/core/renderers/common/path_object.js b/core/renderers/common/path_object.js
index 8e82b2be2..1671f3777 100644
--- a/core/renderers/common/path_object.js
+++ b/core/renderers/common/path_object.js
@@ -181,6 +181,13 @@ Blockly.blockRendering.PathObject.prototype.updateDisabled = function(disabled,
  */
 Blockly.blockRendering.PathObject.prototype.updateSelected = function(enable) {
   this.setClass_('blocklySelected', enable);
+  if (enable) {
+    this.svgPath.setAttribute('stroke', '#fc3');
+    this.svgPath.setAttribute('stroke-width', '3px');
+  } else {
+    this.svgPath.setAttribute('stroke', '');
+    this.svgPath.setAttribute('stroke-width', '');
+  }
 };
 
 /**
diff --git a/core/renderers/zelos/constants.js b/core/renderers/zelos/constants.js
index 8e17d9d69..f12ea22f2 100644
--- a/core/renderers/zelos/constants.js
+++ b/core/renderers/zelos/constants.js
@@ -25,6 +25,7 @@
 goog.provide('Blockly.zelos.ConstantProvider');
 
 goog.require('Blockly.blockRendering.ConstantProvider');
+goog.require('Blockly.utils.dom');
 goog.require('Blockly.utils.object');
 goog.require('Blockly.utils.svgPaths');
 
@@ -79,6 +80,21 @@ Blockly.zelos.ConstantProvider = function() {
    * @override
    */
   this.AFTER_STATEMENT_BOTTOM_ROW_MIN_HEIGHT = this.LARGE_PADDING * 2;
+
+  /**
+   * The ID of the highlight glow filter, or the empty string if no filter is
+   * set.
+   * @type {string}
+   * @package
+   */
+  this.highlightGlowFilterId = '';
+
+  /**
+   * The <filter> element to use for a higlight glow, or null if not set.
+   * @type {SVGElement}
+   * @private
+   */
+  this.highlightGlowFilter_ = null;
 };
 Blockly.utils.object.inherits(Blockly.zelos.ConstantProvider,
     Blockly.blockRendering.ConstantProvider);
@@ -92,6 +108,16 @@ Blockly.zelos.ConstantProvider.prototype.init = function() {
   this.ROUNDED = this.makeRounded();
 };
 
+/**
+ * @override
+ */
+Blockly.zelos.ConstantProvider.prototype.dispose = function() {
+  Blockly.zelos.ConstantProvider.superClass_.dispose.call(this);
+  if (this.highlightGlowFilter_) {
+    Blockly.utils.dom.removeNode(this.highlightGlowFilter_);
+  }
+};
+
 /**
  * @return {!Object} An object containing sizing and path information about
  *     a hexagonal shape for connections.
@@ -298,3 +324,61 @@ Blockly.zelos.ConstantProvider.prototype.makeInsideCorners = function() {
     pathBottomRight: innerBottomRightCorner
   };
 };
+
+/**
+ * @override
+ */
+Blockly.zelos.ConstantProvider.prototype.createDom = function(svg) {
+  Blockly.zelos.ConstantProvider.superClass_.createDom.call(this, svg);
+  /*
+  <defs>
+    ... filters go here ...
+  </defs>
+  */
+  var defs = Blockly.utils.dom.createSvgElement('defs', {}, svg);
+  // Each filter/pattern needs a unique ID for the case of multiple Blockly
+  // instances on a page.  Browser behaviour becomes undefined otherwise.
+  // https://neil.fraser.name/news/2015/11/01/
+  var rnd = String(Math.random()).substring(2);
+  // Using a dilate distorts the block shape.
+  // Instead use a gaussian blur, and then set all alpha to 1 with a transfer.
+  var highlightGlowFilter = Blockly.utils.dom.createSvgElement('filter',
+      {
+        'id': 'blocklyHighlightGlowFilter' + rnd,
+        'height': '160%',
+        'width': '180%',
+        y: '-30%',
+        x: '-40%'
+      },
+      defs);
+  Blockly.utils.dom.createSvgElement('feGaussianBlur',
+      {
+        'in': 'SourceGraphic',
+        'stdDeviation': 0.5  // TODO: configure size in theme.
+      },
+      highlightGlowFilter);
+  // Set all gaussian blur pixels to 1 opacity before applying flood
+  var componentTransfer = Blockly.utils.dom.createSvgElement(
+      'feComponentTransfer', {'result': 'outBlur'}, highlightGlowFilter);
+  Blockly.utils.dom.createSvgElement('feFuncA',
+      {
+        'type': 'table', 'tableValues': '0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1'
+      },
+      componentTransfer);
+  // Color the highlight
+  Blockly.utils.dom.createSvgElement('feFlood',
+      {
+        'flood-color': '#FFF200', // TODO: configure colour in theme.
+        'flood-opacity': 1,
+        'result': 'outColor'
+      },
+      highlightGlowFilter);
+  Blockly.utils.dom.createSvgElement('feComposite',
+      {
+        'in': 'outColor', 'in2': 'outBlur',
+        'operator': 'in', 'result': 'outGlow'
+      },
+      highlightGlowFilter);
+  this.highlightGlowFilterId = highlightGlowFilter.id;
+  this.highlightGlowFilter_ = highlightGlowFilter;
+};
diff --git a/core/renderers/zelos/path_object.js b/core/renderers/zelos/path_object.js
index 8a1383ac6..b0b3b2629 100644
--- a/core/renderers/zelos/path_object.js
+++ b/core/renderers/zelos/path_object.js
@@ -26,6 +26,7 @@ goog.provide('Blockly.zelos.PathObject');
 
 goog.require('Blockly.blockRendering.PathObject');
 goog.require('Blockly.zelos.ConstantProvider');
+goog.require('Blockly.utils.dom');
 goog.require('Blockly.utils.object');
 
 
@@ -46,6 +47,43 @@ Blockly.zelos.PathObject = function(root, constants) {
    * @type {!Blockly.zelos.ConstantProvider}
    */
   this.constants_ = constants;
+
+  /**
+   * The selected path of the block.
+   * @type {SVGElement}
+   * @private
+   */
+  this.svgPathSelected_ = null;
 };
 Blockly.utils.object.inherits(Blockly.zelos.PathObject,
     Blockly.blockRendering.PathObject);
+
+/**
+ * @override
+ */
+Blockly.zelos.PathObject.prototype.setPath = function(pathString) {
+  Blockly.zelos.PathObject.superClass_.setPath.call(this, pathString);
+  if (this.svgPathSelected_) {
+    this.svgPathSelected_.setAttribute('d', pathString);
+  }
+};
+
+/**
+ * @override
+ */
+Blockly.zelos.PathObject.prototype.updateSelected = function(enable) {
+  this.setClass_('blocklySelected', enable);
+  if (enable) {
+    this.svgPathSelected_ =
+      /** @type {!SVGElement} */ (this.svgPath.cloneNode(true));
+    this.svgPathSelected_.setAttribute('fill', 'none');
+    this.svgPathSelected_.setAttribute('filter',
+        'url(#' + this.constants_.highlightGlowFilterId + ')');
+    this.svgRoot.appendChild(this.svgPathSelected_);
+  } else {
+    if (this.svgPathSelected_) {
+      this.svgRoot.removeChild(this.svgPathSelected_);
+      this.svgPathSelected_ = null;
+    }
+  }
+};