diff --git a/requirements.txt b/requirements.txt
index 80ad0d7..7b0cd67 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -8,7 +8,7 @@ google-cloud-core==0.28.1
 google-resumable-media==0.3.1
 googleapis-common-protos==1.5.5
 idna==2.7
-protobuf==3.6.1
+protobuf==3.18.3
 pyasn1==0.4.4
 pyasn1-modules==0.2.2
 pytz==2018.7