diff --git a/setup.cfg b/setup.cfg
index 7180a2ce97..b367dac98a 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -38,7 +38,7 @@ install_requires =
     pandas
     attrs
     dataclasses ; python_version < '3.7'
-    protobuf >=3.5.0.post1 # Per https://github.com/grpc/grpc/blob/v1.45.3/requirements.txt
+    protobuf >=3.5.0.post1, < 5 # Per https://github.com/grpc/grpc/blob/v1.45.3/requirements.txt
     msgpack
     pyyaml
     packaging