diff --git a/README.md b/README.md
index 09aca48..3b30881 100644
--- a/README.md
+++ b/README.md
@@ -19,7 +19,7 @@ The `opts` object can contain:
 Name              | Description                                                    | Default
 ------------------|----------------------------------------------------------------|-----------------------------------
 `level`           | Minimum level to apply anchors on or array of selected levels. | 1
-`slugify`         | A custom slugification function.                               | [string.js' `slugify`][slugify]
+`slugify`         | A custom slugification function.                               | [`slugify`][slugify]
 `permalink`       | Whether to add permalinks next to titles.                      | `false`
 `renderPermalink` | A custom permalink rendering function.                         | See [`index.js`](index.js)
 `permalinkClass`  | The class of the permalink anchor.                             | `header-anchor`
@@ -28,7 +28,7 @@ Name              | Description
 `permalinkHref`   | A custom permalink `href` rendering function.                  | See [`index.js`](index.js)
 `callback`        | Called with token and info after rendering.                    | `undefined`
 
-[slugify]: http://stringjs.com/#methods/slugify
+[slugify]: https://www.npmjs.com/package/slugify
 
 The `renderPermalink` function takes the slug, an options object with
 the above options, and then all the usual markdown-it rendering
diff --git a/index.js b/index.js
index d3d295e..223c805 100644
--- a/index.js
+++ b/index.js
@@ -1,7 +1,6 @@
-const string = require('string')
+const slugifier = require('slugify')
 
-const slugify = s =>
-  string(s).slugify().toString()
+const slugify = s => slugifier(s, {lower: true})
 
 const position = {
   false: 'push',
diff --git a/package.json b/package.json
index d9dbffc..1ea418f 100644
--- a/package.json
+++ b/package.json
@@ -27,7 +27,7 @@
     "test": "npm run lint && node test"
   },
   "dependencies": {
-    "string": "^3.3.3"
+    "slugify": "^1.3.0"
   },
   "devDependencies": {
     "markdown-it": "^8.3.0",