diff --git a/index.js b/index.js
index 7e5643a..9c32e78 100644
--- a/index.js
+++ b/index.js
@@ -1,15 +1,13 @@
 'use strict'
 
 var slugs = require('github-slugger')()
-var visit = require('unist-util-visit')
-var toString = require('hast-util-to-string')
-var is = require('hast-util-is-element')
 var has = require('hast-util-has-property')
+var rank = require('hast-util-heading-rank')
+var toString = require('hast-util-to-string')
+var visit = require('unist-util-visit')
 
 module.exports = slug
 
-var headings = ['h1', 'h2', 'h3', 'h4', 'h5', 'h6']
-
 function slug() {
   return transformer
 }
@@ -18,7 +16,7 @@ function transformer(tree) {
   slugs.reset()
 
   visit(tree, 'element', function (node) {
-    if (is(node, headings) && !has(node, 'id')) {
+    if (rank(node) && !has(node, 'id')) {
       node.properties.id = slugs.slug(toString(node))
     }
   })
diff --git a/package.json b/package.json
index 62a5987..1671d2f 100644
--- a/package.json
+++ b/package.json
@@ -30,7 +30,7 @@
   "dependencies": {
     "github-slugger": "^1.1.1",
     "hast-util-has-property": "^1.0.0",
-    "hast-util-is-element": "^1.0.0",
+    "hast-util-heading-rank": "^1.0.0",
     "hast-util-to-string": "^1.0.0",
     "unist-util-visit": "^2.0.0"
   },