diff --git a/docker/build/installers/py27_requirements.txt b/docker/build/installers/py27_requirements.txt
index a48bb04..8167024 100644
--- a/docker/build/installers/py27_requirements.txt
+++ b/docker/build/installers/py27_requirements.txt
@@ -8,7 +8,7 @@ supervisor
 # Google infras.
 glog
 grpcio-tools == 1.2.0
-protobuf == 3.1
+protobuf == 3.18.3
 python-gflags
 
 # Web utils.