diff --git a/mypy/version.py b/mypy/version.py
index d1a97f6a37da..33da7fb1f3a1 100644
--- a/mypy/version.py
+++ b/mypy/version.py
@@ -1,7 +1,7 @@
 import os
 from mypy import git
 
-__version__ = '0.640-dev'
+__version__ = '0.640+dev'
 base_version = __version__
 
 mypy_dir = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))