diff --git a/package-lock.json b/package-lock.json
index 623d9300..e07b1077 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -528,6 +528,14 @@
       "resolved": "https://registry.npmjs.org/domexception/-/domexception-1.0.0.tgz",
       "integrity": "sha512-WpwuBlZ2lQRFa4H/4w49deb9rJLot9KmqrKKjMc9qBl7CID+DdC2swoa34ccRl+anL2B6bLp6TjFdIdnzekMBQ=="
     },
+    "dot-prop": {
+      "version": "4.2.0",
+      "resolved": "https://registry.npmjs.org/dot-prop/-/dot-prop-4.2.0.tgz",
+      "integrity": "sha512-tUMXrxlExSW6U2EXiiKGSBVdYgtV8qlHL+C10TsW4PURY/ic+eaysnSkwB4kA/mBlCyy/IKDJ+Lc3wbWeaXtuQ==",
+      "requires": {
+        "is-obj": "1.0.1"
+      }
+    },
     "ecc-jsbn": {
       "version": "0.1.1",
       "resolved": "https://registry.npmjs.org/ecc-jsbn/-/ecc-jsbn-0.1.1.tgz",
@@ -1036,6 +1044,11 @@
       "integrity": "sha1-khi5srkoojixPcT7a21XbyMUU+o=",
       "dev": true
     },
+    "indexes-of": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/indexes-of/-/indexes-of-1.0.1.tgz",
+      "integrity": "sha1-8w9xbI4r00bHtn0985FVZqfAVgc="
+    },
     "inflight": {
       "version": "1.0.6",
       "resolved": "https://registry.npmjs.org/inflight/-/inflight-1.0.6.tgz",
@@ -1120,6 +1133,11 @@
         "xtend": "4.0.1"
       }
     },
+    "is-obj": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/is-obj/-/is-obj-1.0.1.tgz",
+      "integrity": "sha1-PkcprB9f3gJc19g6iW2rn09n2w8="
+    },
     "is-path-cwd": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/is-path-cwd/-/is-path-cwd-1.0.0.tgz",
@@ -3458,6 +3476,16 @@
         }
       }
     },
+    "postcss-selector-parser": {
+      "version": "3.1.1",
+      "resolved": "https://registry.npmjs.org/postcss-selector-parser/-/postcss-selector-parser-3.1.1.tgz",
+      "integrity": "sha1-T4dfSvsMllc9XPTXQBGu4lCn6GU=",
+      "requires": {
+        "dot-prop": "4.2.0",
+        "indexes-of": "1.0.1",
+        "uniq": "1.0.1"
+      }
+    },
     "prelude-ls": {
       "version": "1.1.2",
       "resolved": "https://registry.npmjs.org/prelude-ls/-/prelude-ls-1.1.2.tgz",
@@ -3894,6 +3922,11 @@
       "integrity": "sha1-hnrHTjhkGHsdPUfZlqeOxciDB3c=",
       "dev": true
     },
+    "uniq": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/uniq/-/uniq-1.0.1.tgz",
+      "integrity": "sha1-sxxa6CVIRKOoKBVBzisEuGWnNP8="
+    },
     "util-deprecate": {
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/util-deprecate/-/util-deprecate-1.0.2.tgz",
diff --git a/package.json b/package.json
index 4e6f02c8..4d5c6895 100644
--- a/package.json
+++ b/package.json
@@ -45,6 +45,7 @@
     "jsdom": "^11.3.0",
     "lodash": "^4.13.1",
     "postcss": "^6.0.14",
+    "postcss-selector-parser": "3.1.1",
     "request": "^2.72.0"
   },
   "devDependencies": {
diff --git a/src/lib.js b/src/lib.js
index 00231538..2b52c4ae 100644
--- a/src/lib.js
+++ b/src/lib.js
@@ -2,6 +2,7 @@
 
 const jsdom = require('./jsdom.js'),
     postcss = require('postcss'),
+    postcssSelectorParser = require('postcss-selector-parser'),
     _ = require('lodash');
 /* Some styles are applied only with user interaction, and therefore its
  *   selectors cannot be used with querySelectorAll.
@@ -12,7 +13,7 @@ const dePseudify = (function () {
             /* link */
             ':link', ':visited',
             /* user action */
-            ':hover', ':active', ':focus',
+            ':hover', ':active', ':focus', ':focus-within',
             /* UI element states */
             ':enabled', ':disabled', ':checked', ':indeterminate',
             /* form validation */
@@ -28,11 +29,21 @@ const dePseudify = (function () {
              */
             '::?-(?:moz|ms|webkit|o)-[a-z0-9-]+'
         ],
-        // Actual regex is of the format: /([^\\])(:hover|:focus)+/
-        pseudosRegex = new RegExp('([^\\\\])(' + ignoredPseudos.join('|') + ')+');
+        // Actual regex is of the format: /^(:hover|:focus|...)$/i
+        pseudosRegex = new RegExp('^(' + ignoredPseudos.join('|') + ')$', 'i');
+
+    function transform (selectors) {
+        selectors.walkPseudos((selector) => {
+            if (pseudosRegex.test(selector.value)) {
+                selector.remove();
+            }
+        });
+    }
+
+    const processor = postcssSelectorParser(transform);
 
     return function (selector) {
-        return selector.replace(pseudosRegex, '$1');
+        return processor.processSync(selector);
     };
 }());
 
@@ -233,3 +244,5 @@ module.exports = function uncss(pages, css, ignore) {
         }];
     });
 };
+
+module.exports.dePseudify = dePseudify;
diff --git a/tests/depseudify.js b/tests/depseudify.js
new file mode 100644
index 00000000..1a6a90f1
--- /dev/null
+++ b/tests/depseudify.js
@@ -0,0 +1,41 @@
+'use strict';
+
+const expect = require('chai').expect,
+    { dePseudify } = require('../src/lib');
+
+describe('dePseudify() function', () => {
+    const expected = {
+        '.clearfix::before': '.clearfix',
+        '.clearfix:before': '.clearfix',
+        '.sm\\:hover\\:font-hairline': '.sm\\:hover\\:font-hairline',
+        '.sm\\:hover\\:font-hairline:hover': '.sm\\:hover\\:font-hairline',
+        '.sm\\:hover\\:font-hairline\\:hover': '.sm\\:hover\\:font-hairline\\:hover',
+        '.sm\\:hover\\:font-hairline\\:valid': '.sm\\:hover\\:font-hairline\\:valid',
+        '.sm\\:valid\\:font-bold:valid': '.sm\\:valid\\:font-bold',
+        ':focus': '',
+        ':root a:hover': ':root a',
+        ':root': ':root',
+        '[data-text="example of :hover pseudo-class"]:hover': '[data-text="example of :hover pseudo-class"]',
+        'a :not(strong):not(span)': 'a :not(strong):not(span)',
+        'a:hover :not(strong):not(span)': 'a :not(strong):not(span)',
+        'a:nth-child(4n)': 'a:nth-child(4n)',
+        'div:FOCUS-WITHIN': 'div',
+        'div:focus-within': 'div',
+        'h5:hover::before': 'h5',
+        'input:checked ~ label': 'input ~ label',
+        'input:checked ~ label:before': 'input ~ label',
+        'input:nth-child(4n):valid': 'input:nth-child(4n)',
+        'li:only-child': 'li:only-child',
+        'p:hover:not(.fancy)': 'p:not(.fancy)',
+        'p:not(.fancy)': 'p:not(.fancy)',
+        'p:not(.fancy):hover': 'p:not(.fancy)'
+    };
+
+    Object.keys(expected).forEach((input) => {
+        const output = expected[input];
+        it(`should convert ${input} to ${output || '(empty)'}`, (done) => {
+            expect(dePseudify(input)).to.equal(output);
+            done();
+        });
+    });
+});