diff --git a/notebook/_version.py b/notebook/_version.py
index 5a634ac2b3..d1022c0f75 100644
--- a/notebook/_version.py
+++ b/notebook/_version.py
@@ -1,2 +1,13 @@
+"""
+store the current version info of the notebook.
+
+"""
+
+# Downstream maintainer, when running `python.setup.py jsversion`,
+# the version string is propagated to the JavaScript files,  do not forget to
+# patch the JavaScript files in `.postN` release done by distributions. 
+
+# Next beta/alpha/rc release: The version number for beta is X.Y.ZbN **without dots**. 
+
 version_info = (4, 1, 0, 'b1')
-__version__ = '.'.join(map(str, version_info))
+__version__ = '.'.join(map(str, version_info[:3])) + ''.join(version_info[3:])
diff --git a/notebook/tests/test_notebookapp.py b/notebook/tests/test_notebookapp.py
index daf4c4654c..d74857d046 100644
--- a/notebook/tests/test_notebookapp.py
+++ b/notebook/tests/test_notebookapp.py
@@ -3,6 +3,7 @@
 
 import logging
 import os
+import re
 from tempfile import NamedTemporaryFile
 
 import nose.tools as nt
@@ -12,7 +13,7 @@
 from jupyter_core.application import NoStart
 from ipython_genutils.tempdir import TemporaryDirectory
 from traitlets import TraitError
-from notebook import notebookapp
+from notebook import notebookapp, __version__
 NotebookApp = notebookapp.NotebookApp
 
 
@@ -74,4 +75,40 @@ def test_generate_config():
         with nt.assert_raises(NoStart):
             app.start()
         assert os.path.exists(os.path.join(td, 'jupyter_notebook_config.py'))
-    
+
+
+#test if the version testin function works
+def test_pep440_version():
+
+    for version in [
+        '4.1.0.b1',
+        '4.1.b1',
+        '4.2',
+        'X.y.z',
+        '1.2.3.dev1.post2',
+        ]:
+        def loc():
+            with nt.assert_raises(ValueError):
+                raise_on_bad_version(version)
+        yield loc
+
+    for version in [
+        '4.1.1',
+        '4.2.1b3',
+        ]:
+
+        yield (raise_on_bad_version, version)
+
+
+
+pep440re = re.compile('^(\d+)\.(\d+)\.(\d+((a|b|rc)\d+)?)(\.post\d+)?(\.dev\d+)?$')
+
+def raise_on_bad_version(version):
+    if not pep440re.match(version):
+        raise ValueError("Versions String does apparently not match Pep 440 specification, "
+                         "which might lead to sdist and wheel being seen as 2 different release. "
+                         "E.g: do not use dots for beta/alpha/rc markers.")
+
+
+def test_current_version():
+    raise_on_bad_version(__version__)