diff --git a/requirements.txt b/requirements.txt
index f38070a..99fd895 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -8,7 +8,7 @@ google-cloud-datastore==1.6.0
 googleapis-common-protos==1.5.3
 grpcio==1.10.1
 idna==2.6
-protobuf==3.5.2.post1
+protobuf==3.18.3
 pyasn1==0.4.2
 pyasn1-modules==0.2.1
 pytz==2018.3