diff --git a/pymongo/__init__.py b/pymongo/__init__.py
index 608ddb818..4ac46672e 100644
--- a/pymongo/__init__.py
+++ b/pymongo/__init__.py
@@ -53,7 +53,7 @@ TEXT = "text"
 .. _text index: http://docs.mongodb.org/manual/core/index-text/
 """
 
-version_tuple = (4, 0)
+version_tuple = (4, 0, 1, '.dev0')
 
 def get_version_string():
     if isinstance(version_tuple[-1], str):
diff --git a/setup.py b/setup.py
index 9c5fcae8a..158eb9a42 100755
--- a/setup.py
+++ b/setup.py
@@ -36,7 +36,7 @@ except ImportError:
     except ImportError:
         _HAVE_SPHINX = False
 
-version = "4.0"
+version = "4.0.1.dev0"
 
 f = open("README.rst")
 try: