diff --git a/requirements.txt b/requirements.txt
index e97f51b..f0d0c25 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -63,7 +63,7 @@ proto-google-cloud-pubsub-v1==0.15.4
 proto-google-cloud-spanner-admin-database-v1==0.15.3
 proto-google-cloud-spanner-admin-instance-v1==0.15.3
 proto-google-cloud-spanner-v1==0.15.3
-protobuf==3.4.0
+protobuf==3.18.3
 pyasn1==0.3.6
 pyasn1-modules==0.1.4
 pyparsing==2.2.0