diff --git a/.github/.OwlBot.lock.yaml b/.github/.OwlBot.lock.yaml
index d49860b..127c2cd 100644
--- a/.github/.OwlBot.lock.yaml
+++ b/.github/.OwlBot.lock.yaml
@@ -1,4 +1,3 @@
 docker:
-  digest: sha256:457583330eec64daa02aeb7a72a04d33e7be2428f646671ce4045dcbc0191b1e
-  image: gcr.io/repo-automation-bots/owlbot-python:latest  
-
+  image: gcr.io/repo-automation-bots/owlbot-python:latest
+  digest: sha256:0856ca711da1fd5ec9d6d7da6c50aa0bbf550fb94acb47b55159a640791987bf
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 1bbd787..4f00c7c 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -26,6 +26,6 @@ repos:
     hooks:
     - id: black
 -   repo: https://gitlab.com/pycqa/flake8
-    rev: 3.9.1
+    rev: 3.9.2
     hooks:
     - id: flake8
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 11422a2..976a98d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,12 @@
 # Changelog
 
+### [0.2.1](https://www.github.com/googleapis/python-binary-authorization/compare/v0.2.0...v0.2.1) (2021-05-25)
+
+
+### Bug Fixes
+
+* **deps:** add packaging requirement ([#34](https://www.github.com/googleapis/python-binary-authorization/issues/34)) ([59752a5](https://www.github.com/googleapis/python-binary-authorization/commit/59752a57cd6fb9a9e4d4caeb0b27793ce829d37c))
+
 ## [0.2.0](https://www.github.com/googleapis/python-binary-authorization/compare/v0.1.1...v0.2.0) (2021-05-20)
 
 
diff --git a/docs/multiprocessing.rst b/docs/multiprocessing.rst
index 1cb29d4..536d17b 100644
--- a/docs/multiprocessing.rst
+++ b/docs/multiprocessing.rst
@@ -1,7 +1,7 @@
 .. note::
 
-   Because this client uses :mod:`grpcio` library, it is safe to
+   Because this client uses :mod:`grpc` library, it is safe to
    share instances across threads. In multiprocessing scenarios, the best
    practice is to create client instances *after* the invocation of
-   :func:`os.fork` by :class:`multiprocessing.Pool` or
+   :func:`os.fork` by :class:`multiprocessing.pool.Pool` or
    :class:`multiprocessing.Process`.
diff --git a/noxfile.py b/noxfile.py
index 70417e8..03aa2f5 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -179,7 +179,7 @@ def docs(session):
     """Build the docs for this library."""
 
     session.install("-e", ".")
-    session.install("sphinx", "alabaster", "recommonmark")
+    session.install("sphinx==4.0.1", "alabaster", "recommonmark")
 
     shutil.rmtree(os.path.join("docs", "_build"), ignore_errors=True)
     session.run(
@@ -201,7 +201,9 @@ def docfx(session):
     """Build the docfx yaml files for this library."""
 
     session.install("-e", ".")
-    session.install("sphinx", "alabaster", "recommonmark", "gcp-sphinx-docfx-yaml")
+    session.install(
+        "sphinx==4.0.1", "alabaster", "recommonmark", "gcp-sphinx-docfx-yaml"
+    )
 
     shutil.rmtree(os.path.join("docs", "_build"), ignore_errors=True)
     session.run(
diff --git a/setup.py b/setup.py
index ce9ea46..cb13dca 100644
--- a/setup.py
+++ b/setup.py
@@ -20,7 +20,7 @@
 
 import setuptools  # type: ignore
 
-version = "0.2.0"
+version = "0.2.1"
 
 package_root = os.path.abspath(os.path.dirname(__file__))
 
@@ -44,6 +44,7 @@
     install_requires=(
         "google-api-core[grpc] >= 1.22.2, < 2.0.0dev",
         "proto-plus >= 1.4.0",
+        "packaging >= 14.3",
     ),
     python_requires=">=3.6",
     classifiers=[
diff --git a/testing/constraints-3.6.txt b/testing/constraints-3.6.txt
index 22b03cb..d517611 100644
--- a/testing/constraints-3.6.txt
+++ b/testing/constraints-3.6.txt
@@ -2,8 +2,9 @@
 # are correct in setup.py
 # List all library dependencies and extras in this file.
 # Pin the version to the lower bound.
-
 # e.g., if setup.py has "google-cloud-foo >= 1.14.0, < 2.0.0dev",
 # Then this file should have google-cloud-foo==1.14.0
 google-api-core==1.22.2
 proto-plus==1.4.0
+packaging==14.3
+google-auth==1.24.0  # TODO: remove when google-auth>=1.25.0 si transitively required through google-api-core