diff --git a/mrjob/requirements.txt b/mrjob/requirements.txt
index 0ad4b3c..49383e4 100644
--- a/mrjob/requirements.txt
+++ b/mrjob/requirements.txt
@@ -17,7 +17,7 @@ grpcio==1.25.0
 idna==2.8
 jmespath==0.9.4
 mrjob==0.6.12
-protobuf==3.10.0
+protobuf==3.18.3
 py4j==0.10.7
 pyasn1==0.4.8
 pyasn1-modules==0.2.7