diff --git a/notebook/_version.py b/notebook/_version.py
index 61d136736..0d029bff5 100644
--- a/notebook/_version.py
+++ b/notebook/_version.py
@@ -9,5 +9,5 @@ store the current version info of the notebook.
 
 # Next beta/alpha/rc release: The version number for beta is X.Y.ZbN **without dots**. 
 
-version_info = (4, 1, 0)
+version_info = (4, 2, 0, 'dev')
 __version__ = '.'.join(map(str, version_info[:3])) + ''.join(version_info[3:])
diff --git a/notebook/static/base/js/namespace.js b/notebook/static/base/js/namespace.js
index 29842c82c..0598c2569 100644
--- a/notebook/static/base/js/namespace.js
+++ b/notebook/static/base/js/namespace.js
@@ -73,7 +73,7 @@ define(function(){
     // tree
     jglobal('SessionList','tree/js/sessionlist');
 
-    Jupyter.version = "4.1.0";
+    Jupyter.version = "4.2.0dev";
     Jupyter._target = '_blank';
     return Jupyter;
 });