diff --git a/docs/main/changelog.rst b/docs/main/changelog.rst
index ba3de029..85847ea8 100644
--- a/docs/main/changelog.rst
+++ b/docs/main/changelog.rst
@@ -7,6 +7,12 @@ that were made in every particular version.
 From version 0.7.6 *Dependency Injector* framework strictly 
 follows `Semantic versioning`_
 
+4.9.1
+-----
+- Fix a bug in the ``Configuration`` provider to correctly handle undefined values.
+  See issue `#358 <https://github.com/ets-labs/python-dependency-injector/issues/358>`_.
+  Many thanks to `Stefano Frazzetto <https://github.com/StefanoFrazzetto>`_ for reporting the issue.
+
 4.9.0
 -----
 - Add ``.dependencies`` attribute to the ``DeclarativeContainer`` and ``DynamicContainer``.
diff --git a/src/dependency_injector/__init__.py b/src/dependency_injector/__init__.py
index c9f63381..ee8bc44a 100644
--- a/src/dependency_injector/__init__.py
+++ b/src/dependency_injector/__init__.py
@@ -1,6 +1,6 @@
 """Top-level package."""
 
-__version__ = '4.9.0'
+__version__ = '4.9.1'
 """Version number.
 
 :type: str