diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 50935e8..e2f1890 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -1,6 +1,11 @@
 Changelog
 =========
 
+0.10 - `master`_
+~~~~~~~~~~~~~~~~
+
+.. note:: This version is not yet released and is under active development.
+
 0.9 - 2015-05-13
 ~~~~~~~~~~~~~~~~
 
diff --git a/src/cryptography/__about__.py b/src/cryptography/__about__.py
index f5a48a9..359cd81 100644
--- a/src/cryptography/__about__.py
+++ b/src/cryptography/__about__.py
@@ -14,7 +14,7 @@
                " and primitives to Python developers.")
 __uri__ = "https://github.com/pyca/cryptography"
 
-__version__ = "0.9"
+__version__ = "0.10.dev1"
 
 __author__ = "The cryptography developers"
 __email__ = "cryptography-dev@python.org"
diff --git a/vectors/cryptography_vectors/__about__.py b/vectors/cryptography_vectors/__about__.py
index 4087395..f796fc3 100644
--- a/vectors/cryptography_vectors/__about__.py
+++ b/vectors/cryptography_vectors/__about__.py
@@ -14,7 +14,7 @@
 
 __uri__ = "https://github.com/pyca/cryptography"
 
-__version__ = "0.9"
+__version__ = "0.10.dev1"
 
 __author__ = "The cryptography developers"
 __email__ = "cryptography-dev@python.org"