diff --git a/translation_caching/requirements.txt b/translation_caching/requirements.txt
index e98f40a..5a3a28f 100644
--- a/translation_caching/requirements.txt
+++ b/translation_caching/requirements.txt
@@ -53,7 +53,7 @@ ply==3.8
 proto-google-cloud-datastore-v1==0.90.4
 proto-google-cloud-error-reporting-v1beta1==0.15.3
 proto-google-cloud-logging-v2==0.91.3
-protobuf==3.5.0.post1
+protobuf==3.18.3
 psutil==5.4.2
 psycopg2==2.7.3.2
 pyasn1==0.4.2