diff --git a/chapter4/pom.xml b/chapter4/pom.xml
index 3f4c096..a333ea6 100644
--- a/chapter4/pom.xml
+++ b/chapter4/pom.xml
@@ -27,7 +27,7 @@
         <dependency>
             <groupId>com.google.protobuf</groupId>
             <artifactId>protobuf-java</artifactId>
-            <version>3.4.0</version>
+            <version>3.16.3</version>
         </dependency>
         <dependency>
             <groupId>io.netty</groupId>