diff --git a/README.md b/README.md
index 7be8cdb..fb399a2 100644
--- a/README.md
+++ b/README.md
@@ -6,6 +6,10 @@ Declarative client-side transclusion, using [Custom Elements V1](https://develop
 
 Based on [hinclude.js](https://github.com/mnot/hinclude) by [@mnot](https://github.com/mnot/).
 
+*Breaking changes in version 4.0.0*:
+
+Rename `alt` attribute to `when-false-src` to support future feature for error handling.
+
 *Breaking changes in version 3.0.0*:
 
 - Because h-include is now using Custom Elements V1, we recommend that you update your polyfill (i.e. [document-register-element](https://github.com/WebReflection/document-register-element)) to the latest version.
diff --git a/bower.json b/bower.json
index 97c88c3..b87d6a7 100644
--- a/bower.json
+++ b/bower.json
@@ -1,6 +1,6 @@
 {
   "name": "h-include",
-  "version": "3.1.1",
+  "version": "4.0.0",
   "main": "h-include.js",
   "keywords": [
     "web-components"
diff --git a/h-include.js b/h-include.js
index a38e947..6d3c838 100644
--- a/h-include.js
+++ b/h-include.js
@@ -20,7 +20,7 @@ console.warn('Using h-include.js from the root folder is deprecated, please use
 })();
 
 /*
-h-include.js -- HTML Includes (version 3.1.1)
+h-include.js -- HTML Includes (version 4.0.0)
 
 MIT Style License
 
diff --git a/lib/h-include.js b/lib/h-include.js
index 1dc2a71..e8e405e 100644
--- a/lib/h-include.js
+++ b/lib/h-include.js
@@ -17,7 +17,7 @@
 })();
 
 /*
-h-include.js -- HTML Includes (version 3.1.1)
+h-include.js -- HTML Includes (version 4.0.0)
 
 MIT Style License
 
diff --git a/package.json b/package.json
index 2f1a91f..8617874 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "h-include",
-  "version": "3.1.1",
+  "version": "4.0.0",
   "homepage": "https://github.com/gustafnk/h-include",
   "repository": {
     "type": "git",