diff --git a/requirements.txt b/requirements.txt
index 8a217cf085722c94a6383012cf00e2098b7586ff..48032ded8bf2db44526f555950865e6faf9d7df4 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,6 @@
 astropy>=4.0
 grpcio>=1.28.1
 orjson>=3.0.2
+protobuf==3.9.0
 git+https://github.com/astronomical-data-processing/csst-dfs-proto-py.git
 git+https://github.com/astronomical-data-processing/csst-dfs-commons.git
\ No newline at end of file