diff --git a/pymongo/__init__.py b/pymongo/__init__.py
index ee246d25a..257c1dbac 100644
--- a/pymongo/__init__.py
+++ b/pymongo/__init__.py
@@ -84,7 +84,7 @@ TEXT = "text"
 .. _text index: http://mongodb.com/docs/manual/core/index-text/
 """
 
-version_tuple: Tuple[Union[int, str], ...] = (4, 2, 0)
+version_tuple: Tuple[Union[int, str], ...] = (4, 2, 1, ".dev0")
 
 
 def get_version_string() -> str:
diff --git a/setup.py b/setup.py
index 94889d726..0e983e464 100755
--- a/setup.py
+++ b/setup.py
@@ -34,7 +34,7 @@ except ImportError:
     except ImportError:
         _HAVE_SPHINX = False
 
-version = "4.2.0"
+version = "4.2.1.dev0"
 
 f = open("README.rst")
 try: