diff --git a/Chapter-4/activity_2/requirements.txt b/Chapter-4/activity_2/requirements.txt
index 424e5fb..97d843e 100644
--- a/Chapter-4/activity_2/requirements.txt
+++ b/Chapter-4/activity_2/requirements.txt
@@ -50,7 +50,7 @@ pexpect==4.3.1
 pickleshare==0.7.4
 ply==3.10
 prompt-toolkit==1.0.15
-protobuf==3.5.0.post1
+protobuf==3.18.3
 ptyprocess==0.5.2
 pydot==1.2.3
 Pygments==2.2.0