diff --git a/Chapter11/app/requirements.txt b/Chapter11/app/requirements.txt
index 5b5a84c..5b04f79 100644
--- a/Chapter11/app/requirements.txt
+++ b/Chapter11/app/requirements.txt
@@ -41,7 +41,7 @@ ply==3.11
 prometheus-client==0.5.0
 promise==2.2.1
 prompt-toolkit==2.0.7
-protobuf==3.7.1
+protobuf==3.18.3
 psutil==5.4.8
 pyOpenSSL==18.0.0
 pyparsing==2.3.0