diff --git a/cmd/suggestion/optuna/v1beta1/requirements.txt b/cmd/suggestion/optuna/v1beta1/requirements.txt
index a7855779b2c..5666d131399 100644
--- a/cmd/suggestion/optuna/v1beta1/requirements.txt
+++ b/cmd/suggestion/optuna/v1beta1/requirements.txt
@@ -1,4 +1,4 @@
 grpcio==1.41.1
-protobuf==3.19.1
+protobuf==3.19.5
 googleapis-common-protos==1.53.0
 optuna>=3.0.0