diff --git a/bower.json b/bower.json
index 8edaf37e95dd170591bbbb37f0f0eca941981183..ac038a783f5c553329de6c77a47e0ae0edd357a4 100644
--- a/bower.json
+++ b/bower.json
@@ -1,6 +1,6 @@
 {
   "name": "reveal.js",
-  "version": "3.9.1",
+  "version": "4.0.0-dev",
   "main": [
     "js/reveal.js",
     "css/reveal.css"
diff --git a/js/reveal.js b/js/reveal.js
index 28c31023a9ec9413567a34bec3522f1668e0f894..997452690d5bd5116d3b042bc849ebc736db9279 100644
--- a/js/reveal.js
+++ b/js/reveal.js
@@ -26,7 +26,7 @@
 	var Reveal;
 
 	// The reveal.js version
-	var VERSION = '3.9.1';
+	var VERSION = '4.0.0-dev';
 
 	var SLIDES_SELECTOR = '.slides section',
 		HORIZONTAL_SLIDES_SELECTOR = '.slides>section',
diff --git a/package-lock.json b/package-lock.json
index 5a1d393bbe67e30fa86888a7381db47f0964cbc1..a1ec366f42a3d2ae3b2db91962768ae749b2cd72 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "reveal.js",
-  "version": "3.9.1",
+  "version": "4.0.0-dev",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
diff --git a/package.json b/package.json
index 4898ed2c9da6f4c7f4d627dce602775468e73139..07b60893406a2d7793cdcdc579c6198f38a86ae0 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "reveal.js",
-  "version": "3.9.1",
+  "version": "4.0.0-dev",
   "description": "The HTML Presentation Framework",
   "homepage": "http://revealjs.com",
   "subdomain": "revealjs",