diff --git a/.eslintrc.js b/.eslintrc.js
index 71a39bc1ca..37592b6609 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -59,13 +59,37 @@ module.exports = {
         selector: 'MemberExpression[property.name=tagName]',
         message: "Don't use node.tagName, use node.nodeName instead."
       },
+      // node.attributes can be clobbered so is unsafe to use
+      // @see https://github.com/dequelabs/axe-core/pull/1432
       {
-        // node.attributes can be clobbered so is unsafe to use
-        // @see https://github.com/dequelabs/axe-core/pull/1432
+        // node.attributes
         selector:
           'MemberExpression[object.name=node][property.name=attributes]',
         message:
           "Don't use node.attributes, use node.hasAttributes() or axe.utils.getNodeAttributes(node) instead."
+      },
+      {
+        // vNode.actualNode.attributes
+        selector:
+          'MemberExpression[object.property.name=actualNode][property.name=attributes]',
+        message:
+          "Don't use node.attributes, use node.hasAttributes() or axe.utils.getNodeAttributes(node) instead."
+      },
+      // node.contains doesn't work with shadow dom
+      // @see https://github.com/dequelabs/axe-core/issues/4194
+      {
+        // node.contains()
+        selector:
+          'CallExpression[callee.object.name=node][callee.property.name=contains]',
+        message:
+          "Don't use node.contains(node2) as it doesn't work across shadow DOM. Use axe.utils.contains(node, node2) instead."
+      },
+      {
+        // vNode.actualNode.contains()
+        selector:
+          'CallExpression[callee.object.property.name=actualNode][callee.property.name=contains]',
+        message:
+          "Don't use node.contains(node2) as it doesn't work across shadow DOM. Use axe.utils.contains(node, node2) instead."
       }
     ]
   },
diff --git a/lib/checks/mobile/target-size-evaluate.js b/lib/checks/mobile/target-size-evaluate.js
index 85561055b2..88c029f34e 100644
--- a/lib/checks/mobile/target-size-evaluate.js
+++ b/lib/checks/mobile/target-size-evaluate.js
@@ -5,6 +5,7 @@ import {
   rectHasMinimumSize,
   hasVisualOverlap
 } from '../../commons/math';
+import { contains } from '../../core/utils';
 
 /**
  * Determine if an element has a minimum size, taking into account
@@ -187,9 +188,7 @@ function toDecimalSize(rect) {
 }
 
 function isDescendantNotInTabOrder(vAncestor, vNode) {
-  return (
-    vAncestor.actualNode.contains(vNode.actualNode) && !isInTabOrder(vNode)
-  );
+  return contains(vAncestor, vNode) && !isInTabOrder(vNode);
 }
 
 function mapActualNodes(vNodes) {
diff --git a/lib/commons/dom/get-target-rects.js b/lib/commons/dom/get-target-rects.js
index fc5b2aabe7..a2bc2eec12 100644
--- a/lib/commons/dom/get-target-rects.js
+++ b/lib/commons/dom/get-target-rects.js
@@ -2,6 +2,7 @@ import findNearbyElms from './find-nearby-elms';
 import isInTabOrder from './is-in-tab-order';
 import { splitRects, hasVisualOverlap } from '../math';
 import memoize from '../../core/utils/memoize';
+import { contains } from '../../core/utils';
 
 export default memoize(getTargetRects);
 
@@ -32,7 +33,5 @@ function getTargetRects(vNode) {
 }
 
 function isDescendantNotInTabOrder(vAncestor, vNode) {
-  return (
-    vAncestor.actualNode.contains(vNode.actualNode) && !isInTabOrder(vNode)
-  );
+  return contains(vAncestor, vNode) && !isInTabOrder(vNode);
 }
diff --git a/lib/core/utils/contains.js b/lib/core/utils/contains.js
index dfea001e1f..6b05722c0b 100644
--- a/lib/core/utils/contains.js
+++ b/lib/core/utils/contains.js
@@ -12,8 +12,10 @@ export default function contains(vNode, otherVNode) {
     !vNode.shadowId &&
     !otherVNode.shadowId &&
     vNode.actualNode &&
+    // eslint-disable-next-line no-restricted-syntax
     typeof vNode.actualNode.contains === 'function'
   ) {
+    // eslint-disable-next-line no-restricted-syntax
     return vNode.actualNode.contains(otherVNode.actualNode);
   }
 
diff --git a/test/checks/mobile/target-size.js b/test/checks/mobile/target-size.js
index 688f809753..f0769c3c54 100644
--- a/test/checks/mobile/target-size.js
+++ b/test/checks/mobile/target-size.js
@@ -1,23 +1,22 @@
-describe('target-size tests', function () {
-  'use strict';
-
-  var checkContext = axe.testUtils.MockCheckContext();
-  var checkSetup = axe.testUtils.checkSetup;
-  var shadowCheckSetup = axe.testUtils.shadowCheckSetup;
-  var check = checks['target-size'];
+describe('target-size tests', () => {
+  const checkContext = axe.testUtils.MockCheckContext();
+  const checkSetup = axe.testUtils.checkSetup;
+  const shadowCheckSetup = axe.testUtils.shadowCheckSetup;
+  const check = checks['target-size'];
+  const fixture = document.querySelector('#fixture');
 
   function elmIds(elms) {
-    return Array.from(elms).map(function (elm) {
+    return Array.from(elms).map(elm => {
       return '#' + elm.id;
     });
   }
 
-  afterEach(function () {
+  afterEach(() => {
     checkContext.reset();
   });
 
-  it('returns false for targets smaller than minSize', function () {
-    var checkArgs = checkSetup(
+  it('returns false for targets smaller than minSize', () => {
+    const checkArgs = checkSetup(
       '<button id="target" style="' +
         'display: inline-block; width:20px; height:30px;' +
         '">x</button>'
@@ -30,8 +29,8 @@ describe('target-size tests', function () {
     });
   });
 
-  it('returns undefined for non-tabbable targets smaller than minSize', function () {
-    var checkArgs = checkSetup(
+  it('returns undefined for non-tabbable targets smaller than minSize', () => {
+    const checkArgs = checkSetup(
       '<button id="target" tabindex="-1" style="' +
         'display: inline-block; width:20px; height:30px;' +
         '">x</button>'
@@ -44,8 +43,8 @@ describe('target-size tests', function () {
     });
   });
 
-  it('returns true for unobscured targets larger than minSize', function () {
-    var checkArgs = checkSetup(
+  it('returns true for unobscured targets larger than minSize', () => {
+    const checkArgs = checkSetup(
       '<button id="target" style="' +
         'display: inline-block; width:40px; height:30px;' +
         '">x</button>'
@@ -58,8 +57,8 @@ describe('target-size tests', function () {
     });
   });
 
-  it('returns true for very large targets', function () {
-    var checkArgs = checkSetup(
+  it('returns true for very large targets', () => {
+    const checkArgs = checkSetup(
       '<button id="target" style="' +
         'display: inline-block; width:240px; height:300px;' +
         '">x</button>'
@@ -68,9 +67,9 @@ describe('target-size tests', function () {
     assert.deepEqual(checkContext._data, { messageKey: 'large', minSize: 24 });
   });
 
-  describe('when fully obscured', function () {
-    it('returns true, regardless of size', function () {
-      var checkArgs = checkSetup(
+  describe('when fully obscured', () => {
+    it('returns true, regardless of size', () => {
+      const checkArgs = checkSetup(
         '<a href="#" id="target" style="' +
           'display: inline-block; width:20px; height:20px;' +
           '">x</a>' +
@@ -83,8 +82,8 @@ describe('target-size tests', function () {
       assert.deepEqual(elmIds(checkContext._relatedNodes), ['#obscurer']);
     });
 
-    it('returns true when obscured by another focusable widget', function () {
-      var checkArgs = checkSetup(
+    it('returns true when obscured by another focusable widget', () => {
+      const checkArgs = checkSetup(
         '<a href="#" id="target" style="' +
           'display: inline-block; width:20px; height:20px;' +
           '">x</a>' +
@@ -97,8 +96,8 @@ describe('target-size tests', function () {
       assert.deepEqual(elmIds(checkContext._relatedNodes), ['#obscurer']);
     });
 
-    it('ignores obscuring element has pointer-events:none', function () {
-      var checkArgs = checkSetup(
+    it('ignores obscuring element has pointer-events:none', () => {
+      const checkArgs = checkSetup(
         '<a href="#" id="target" style="' +
           'display: inline-block; width:20px; height:20px;' +
           '">x</a>' +
@@ -115,9 +114,9 @@ describe('target-size tests', function () {
     });
   });
 
-  describe('when partially obscured', function () {
-    it('returns true for focusable non-widgets', function () {
-      var checkArgs = checkSetup(
+  describe('when partially obscured', () => {
+    it('returns true for focusable non-widgets', () => {
+      const checkArgs = checkSetup(
         '<button id="target" style="' +
           'display: inline-block; width:40px; height:30px; margin-left:30px;' +
           '">x</button>' +
@@ -137,8 +136,8 @@ describe('target-size tests', function () {
       assert.deepEqual(elmIds(checkContext._relatedNodes), ['#obscurer']);
     });
 
-    it('returns true for non-focusable widgets', function () {
-      var checkArgs = checkSetup(
+    it('returns true for non-focusable widgets', () => {
+      const checkArgs = checkSetup(
         '<button id="target" style="' +
           'display: inline-block; width:40px; height:30px; margin-left:30px;' +
           '">x</button>' +
@@ -158,9 +157,9 @@ describe('target-size tests', function () {
       assert.deepEqual(elmIds(checkContext._relatedNodes), ['#obscurer']);
     });
 
-    describe('by a focusable widget', function () {
-      it('returns true for obscured targets with sufficient space', function () {
-        var checkArgs = checkSetup(
+    describe('by a focusable widget', () => {
+      it('returns true for obscured targets with sufficient space', () => {
+        const checkArgs = checkSetup(
           '<button id="target" style="' +
             'display: inline-block; width:40px; height:30px;' +
             '">x</button>' +
@@ -202,8 +201,8 @@ describe('target-size tests', function () {
       });
 
       describe('for obscured targets with insufficient space', () => {
-        it('returns false if all elements are tabbable', function () {
-          var checkArgs = checkSetup(
+        it('returns false if all elements are tabbable', () => {
+          const checkArgs = checkSetup(
             '<button id="target" style="' +
               'display: inline-block; width:40px; height:30px; margin-left:30px;' +
               '">x</button>' +
@@ -227,8 +226,8 @@ describe('target-size tests', function () {
           ]);
         });
 
-        it('returns undefined if the target is not tabbable', function () {
-          var checkArgs = checkSetup(
+        it('returns undefined if the target is not tabbable', () => {
+          const checkArgs = checkSetup(
             '<button id="target" tabindex="-1" style="' +
               'display: inline-block; width:40px; height:30px; margin-left:30px;' +
               '">x</button>' +
@@ -252,8 +251,8 @@ describe('target-size tests', function () {
           ]);
         });
 
-        it('returns undefined if the obscuring node is not tabbable', function () {
-          var checkArgs = checkSetup(
+        it('returns undefined if the obscuring node is not tabbable', () => {
+          const checkArgs = checkSetup(
             '<button id="target" style="' +
               'display: inline-block; width:40px; height:30px; margin-left:30px;' +
               '">x</button>' +
@@ -279,8 +278,8 @@ describe('target-size tests', function () {
       });
 
       describe('that is a descendant', () => {
-        it('returns false if the widget is tabbable', function () {
-          var checkArgs = checkSetup(
+        it('returns false if the widget is tabbable', () => {
+          const checkArgs = checkSetup(
             `<a role="link" aria-label="play" tabindex="0" style="display:inline-block" id="target">
               <button style="margin:1px; line-height:20px">Play</button>
             </a>`
@@ -289,8 +288,8 @@ describe('target-size tests', function () {
           assert.isFalse(out);
         });
 
-        it('returns true if the widget is not tabbable', function () {
-          var checkArgs = checkSetup(
+        it('returns true if the widget is not tabbable', () => {
+          const checkArgs = checkSetup(
             `<a role="link" aria-label="play" tabindex="0" style="display:inline-block" id="target">
               <button tabindex="-1" style="margin:1px; line-height:20px">Play</button>
             </a>`
@@ -301,8 +300,8 @@ describe('target-size tests', function () {
       });
 
       describe('that is a descendant', () => {
-        it('returns false if the widget is tabbable', function () {
-          var checkArgs = checkSetup(
+        it('returns false if the widget is tabbable', () => {
+          const checkArgs = checkSetup(
             `<a role="link" aria-label="play" tabindex="0" style="display:inline-block" id="target">
               <button style="margin:1px; line-height:20px">Play</button>
             </a>`
@@ -311,8 +310,8 @@ describe('target-size tests', function () {
           assert.isFalse(out);
         });
 
-        it('returns true if the widget is not tabbable', function () {
-          var checkArgs = checkSetup(
+        it('returns true if the widget is not tabbable', () => {
+          const checkArgs = checkSetup(
             `<a role="link" aria-label="play" tabindex="0" style="display:inline-block" id="target">
               <button tabindex="-1" style="margin:1px; line-height:20px">Play</button>
             </a>`
@@ -324,9 +323,9 @@ describe('target-size tests', function () {
     });
   });
 
-  describe('with overflowing content', function () {
+  describe('with overflowing content', () => {
     it('returns undefined target is too small', () => {
-      var checkArgs = checkSetup(
+      const checkArgs = checkSetup(
         '<a href="#" id="target"><img width="24" height="24"></a>'
       );
       assert.isUndefined(check.evaluate.apply(checkContext, checkArgs));
@@ -337,7 +336,7 @@ describe('target-size tests', function () {
     });
 
     it('returns true if target has sufficient size', () => {
-      var checkArgs = checkSetup(
+      const checkArgs = checkSetup(
         '<a href="#" id="target" style="font-size:24px;"><img width="24" height="24"></a>'
       );
       assert.isTrue(check.evaluate.apply(checkContext, checkArgs));
@@ -345,7 +344,7 @@ describe('target-size tests', function () {
 
     describe('and partially obscured', () => {
       it('is undefined when unobscured area is too small', () => {
-        var checkArgs = checkSetup(
+        const checkArgs = checkSetup(
           '<a href="#" id="target" style="font-size:24px;">' +
             '  <img width="24" height="36" style="vertical-align: bottom;">' +
             '</a><br>' +
@@ -359,7 +358,7 @@ describe('target-size tests', function () {
       });
 
       it('is true when unobscured area is sufficient', () => {
-        var checkArgs = checkSetup(
+        const checkArgs = checkSetup(
           '<a href="#" id="target" style="font-size:24px;">' +
             '  <img width="24" height="36" style="vertical-align: bottom;">' +
             '</a><br>' +
@@ -371,7 +370,7 @@ describe('target-size tests', function () {
 
     describe('and fully obscured', () => {
       it('is undefined', () => {
-        var checkArgs = checkSetup(
+        const checkArgs = checkSetup(
           '<a href="#" id="target" style="font-size:24px;">' +
             '  <img width="24" height="36" style="vertical-align: bottom;">' +
             '</a><br>' +
@@ -386,8 +385,8 @@ describe('target-size tests', function () {
     });
   });
 
-  it('works across shadow boundaries', function () {
-    var checkArgs = shadowCheckSetup(
+  it('works across shadow boundaries', () => {
+    const checkArgs = shadowCheckSetup(
       '<span id="shadow"></span>' +
         '<button id="obscurer1" style="' +
         'display: inline-block; width:40px; height:30px; margin-left: -10px;' +
@@ -411,4 +410,19 @@ describe('target-size tests', function () {
       '#obscurer2'
     ]);
   });
+
+  it('ignores descendants of the target that are in shadow dom', () => {
+    fixture.innerHTML =
+      '<button id="target" style="width: 30px; height: 40px; position: absolute; left: 10px; top: 5px"><span id="shadow"></span></button>';
+    const target = fixture.querySelector('#target');
+    const shadow = fixture
+      .querySelector('#shadow')
+      .attachShadow({ mode: 'open' });
+    shadow.innerHTML =
+      '<div style="position: absolute; left: 5px; top: 5px; width: 50px; height: 50px;"></div>';
+
+    axe.setup(fixture);
+    const vNode = axe.utils.getNodeFromTree(target);
+    assert.isTrue(check.evaluate.apply(checkContext, [target, {}, vNode]));
+  });
 });
diff --git a/test/commons/dom/get-target-rects.js b/test/commons/dom/get-target-rects.js
index f25abe2918..be37b7cbb6 100644
--- a/test/commons/dom/get-target-rects.js
+++ b/test/commons/dom/get-target-rects.js
@@ -1,6 +1,7 @@
 describe('get-target-rects', () => {
   const getTargetRects = axe.commons.dom.getTargetRects;
   const { queryFixture } = axe.testUtils;
+  const fixture = document.getElementById('fixture');
 
   it('returns the bounding rect when unobscured', () => {
     const vNode = queryFixture('<button id="target">x</button>');
@@ -74,10 +75,25 @@ describe('get-target-rects', () => {
       </button>
     `);
     const rects = getTargetRects(vNode);
-    console.log(JSON.stringify(rects));
     assert.deepEqual(rects, [
       new DOMRect(10, 5, 30, 7),
       new DOMRect(10, 5, 7, 40)
     ]);
   });
+
+  it('ignores non-tabbable descendants of the target that are in shadow dom', () => {
+    fixture.innerHTML =
+      '<button id="target" style="width: 30px; height: 40px; position: absolute; left: 10px; top: 5px"><span id="shadow"></span></button>';
+    const target = fixture.querySelector('#target');
+    const shadow = fixture
+      .querySelector('#shadow')
+      .attachShadow({ mode: 'open' });
+    shadow.innerHTML =
+      '<div style="position: absolute; left: 5px; top: 5px; width: 50px; height: 50px;"></div>';
+
+    axe.setup(fixture);
+    const vNode = axe.utils.getNodeFromTree(target);
+    const rects = getTargetRects(vNode);
+    assert.deepEqual(rects, [vNode.actualNode.getBoundingClientRect()]);
+  });
 });
diff --git a/test/integration/full/target-size/shadow-dom.html b/test/integration/full/target-size/shadow-dom.html
new file mode 100644
index 0000000000..cc5e33f732
--- /dev/null
+++ b/test/integration/full/target-size/shadow-dom.html
@@ -0,0 +1,66 @@
+<!doctype html>
+<html lang="en">
+  <head>
+    <title>Target-size shadow DOM test</title>
+    <link
+      rel="stylesheet"
+      type="text/css"
+      href="/node_modules/mocha/mocha.css"
+    />
+    <script src="/node_modules/mocha/mocha.js"></script>
+    <script src="/node_modules/chai/chai.js"></script>
+    <script src="/axe.js"></script>
+    <script>
+      mocha.setup({
+        timeout: 10000,
+        ui: 'bdd'
+      });
+      var assert = chai.assert;
+    </script>
+  </head>
+  <body>
+    <main id="mocha"></main>
+    <script>
+      const shadowTemplate = document.createElement('template');
+      shadowTemplate.innerHTML =
+        '<div id="shadow-container"><slot></slot></div>';
+      class ShadowOpenWebComponent extends HTMLElement {
+        connectedCallback() {
+          const shadowRoot = this.attachShadow({ mode: 'open' });
+          shadowRoot.appendChild(shadowTemplate.content.cloneNode(true));
+        }
+      }
+
+      customElements.define('shadow-open', ShadowOpenWebComponent);
+    </script>
+    <style>
+      #container {
+        font-size: 16px;
+      }
+      #title {
+        background-color: #cff;
+      }
+      #content {
+        background-color: #cfc;
+        margin-top: 10px;
+      }
+    </style>
+    <div id="container">
+      <div id="title">
+        <a id="title-link" href="#target">
+          <shadow-open>
+            <div>Title</div>
+          </shadow-open>
+        </a>
+      </div>
+      <div id="content">
+        <a id="content-link" href="#target">
+          <div>Content</div>
+        </a>
+      </div>
+    </div>
+    <script src="/test/testutils.js"></script>
+    <script src="shadow-dom.js"></script>
+    <script src="/test/integration/adapter.js"></script>
+  </body>
+</html>
diff --git a/test/integration/full/target-size/shadow-dom.js b/test/integration/full/target-size/shadow-dom.js
new file mode 100644
index 0000000000..557ad32f94
--- /dev/null
+++ b/test/integration/full/target-size/shadow-dom.js
@@ -0,0 +1,39 @@
+describe('target-size shadow dom test', () => {
+  'use strict';
+  let results;
+
+  before(done => {
+    axe.testUtils.awaitNestedLoad(async () => {
+      const options = {
+        runOnly: ['target-size'],
+        elementRef: true
+      };
+      const context = {
+        // ignore the mocha links
+        exclude: '#mocha'
+      };
+      results = await axe.run(context, options);
+      done();
+    });
+  });
+
+  describe('violations', function () {
+    it('should find 0', function () {
+      assert.lengthOf(results.violations, 0);
+    });
+  });
+
+  describe('passes', function () {
+    it('should find 2', function () {
+      assert.lengthOf(results.passes[0].nodes, 2);
+    });
+  });
+
+  it('should find 0 inapplicable', function () {
+    assert.lengthOf(results.inapplicable, 0);
+  });
+
+  it('should find 0 incomplete', function () {
+    assert.lengthOf(results.incomplete, 0);
+  });
+});