diff --git a/RELEASE.md b/RELEASE.md
index 4cc5782..3f03e18 100644
--- a/RELEASE.md
+++ b/RELEASE.md
@@ -1,3 +1,21 @@
+# Version 1.21.1
+
+## Major Features and Improvements
+
+*   N/A
+
+## Bug Fixes and Other Changes
+
+*   Align pip package protobuf dependency requirement to `protobuf>=6.31.1,<7` to match compiled C++ extensions.
+
+## Breaking Changes
+
+*   N/A
+
+## Deprecations
+
+*   N/A
+
 # Version 1.21.0
 
 ## Major Features and Improvements
diff --git a/setup.py b/setup.py
index 9c2a17f..cf7af08 100644
--- a/setup.py
+++ b/setup.py
@@ -136,8 +136,7 @@ def run(self):
     install_requires=[
         "absl-py>=0.9,<3.0.0",
         'googleapis-common-protos>=1.56.4,<2;python_version>="3.11"',
-        'protobuf>=4.25.2;python_version>="3.11"',
-        'protobuf>=4.21.6,<=6.32;python_version<"3.11"',
+        "protobuf>=6.31.1,<7",
     ],
     python_requires=">=3.10,<4",
     packages=find_packages(),
diff --git a/tensorflow_metadata/version.py b/tensorflow_metadata/version.py
index 66f9960..5baf9ef 100644
--- a/tensorflow_metadata/version.py
+++ b/tensorflow_metadata/version.py
@@ -14,4 +14,4 @@
 """Contains the version string of TFMD."""
 
 # Note that setup.py uses this version.
-__version__ = "1.21.0"
+__version__ = "1.21.1"