diff --git a/cirq-google/requirements.txt b/cirq-google/requirements.txt
index f2d74cc1d55..39c5cbeba36 100644
--- a/cirq-google/requirements.txt
+++ b/cirq-google/requirements.txt
@@ -1,3 +1,3 @@
 google-api-core[grpc] >= 1.14.0
 proto-plus >= 1.20.0
-protobuf >= 3.15.0
+protobuf >= 3.15.0, < 5.0.0
diff --git a/dev_tools/requirements/deps/mypy.txt b/dev_tools/requirements/deps/mypy.txt
index 2597cc8a8e4..e89fad986af 100644
--- a/dev_tools/requirements/deps/mypy.txt
+++ b/dev_tools/requirements/deps/mypy.txt
@@ -4,6 +4,6 @@ mypy==1.2.0
 # packages with stub types for various libraries
 types-backports==0.1.3
 types-cachetools
-types-protobuf~=3.20
+types-protobuf>=3.20.0,<5.0.0
 types-requests==2.28.1
 types-setuptools==62.6.1
diff --git a/dev_tools/requirements/deps/protos.txt b/dev_tools/requirements/deps/protos.txt
index 20ec6b9f200..011cf96756d 100644
--- a/dev_tools/requirements/deps/protos.txt
+++ b/dev_tools/requirements/deps/protos.txt
@@ -3,4 +3,4 @@
 # This bundles protoc 3.24.3, which we use for generating proto code.
 grpcio-tools~=1.59.0
 
-mypy-protobuf==3.4
+mypy-protobuf~=3.4