diff --git a/package.json b/package.json
index 68ea8fd..3ca6f39 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "unist-util-size",
-  "version": "3.0.1",
+  "version": "4.0.0",
   "description": "unist utility to calculate the number of nodes in a tree",
   "license": "MIT",
   "keywords": [
diff --git a/readme.md b/readme.md
index b76b93e..ad3e8f9 100644
--- a/readme.md
+++ b/readme.md
@@ -46,14 +46,14 @@ npm install unist-util-size
 In Deno with [`esm.sh`][esmsh]:
 
 ```js
-import {size} from 'https://esm.sh/unist-util-size@3'
+import {size} from 'https://esm.sh/unist-util-size@4'
 ```
 
 In browsers with [`esm.sh`][esmsh]:
 
 ```html
 <script type="module">
-  import {size} from 'https://esm.sh/unist-util-size@3?bundle'
+  import {size} from 'https://esm.sh/unist-util-size@4?bundle'
 </script>
 ```