diff --git a/legacy/requirements.txt b/legacy/requirements.txt
index fd5b57e..926f709 100644
--- a/legacy/requirements.txt
+++ b/legacy/requirements.txt
@@ -46,7 +46,7 @@ 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==3.5.1
+protobuf==3.15.0
 psutil==5.4.3
 pyasn1==0.4.2
 pyasn1-modules==0.2.1