diff --git a/online-boutique-demo/src/emailservice/requirements.txt b/online-boutique-demo/src/emailservice/requirements.txt
index 0bf8440..2f1cca0 100644
--- a/online-boutique-demo/src/emailservice/requirements.txt
+++ b/online-boutique-demo/src/emailservice/requirements.txt
@@ -71,7 +71,7 @@ opencensus==0.7.11
     #   -r requirements.in
     #   opencensus-ext-grpc
     #   opencensus-ext-stackdriver
-protobuf==3.13.0
+protobuf==6.33.5
     # via
     #   google-api-core
     #   google-cloud-profiler