diff --git a/RELEASE.md b/RELEASE.md
index 5a4cc640c..2920efca3 100644
--- a/RELEASE.md
+++ b/RELEASE.md
@@ -8,6 +8,9 @@
 
 ## Bug Fixed and Other Changes
 
+*   Depends on `protobuf>=4.25.2,<5` for Python 3.11 and on `protobuf>4.21.6,<5`
+    for 3.9 and 3.10.
+
 # Version 1.16.0
 
 ## Major Features and Improvements
diff --git a/setup.py b/setup.py
index 5b1ad7415..6382725a5 100644
--- a/setup.py
+++ b/setup.py
@@ -166,7 +166,7 @@ def run(self):
         'absl-py>=0.9,<2.0.0',
         'attrs>=20.3,<24',
         'grpcio>=1.8.6,<2',
-        f'protobuf>={"4.25.2" if _IS_PY311 else "3.20.3"},<5',
+        f'protobuf>={"4.25.2" if _IS_PY311 else "4.21.6"},<5',
         'six>=1.10,<2',
     ],
     extras_require={