diff --git a/Part-4/part04-Part04_21.NumberOfStrings/pom.xml b/Part-4/part04-Part04_21.NumberOfStrings/pom.xml
index 7a56e59..d35546f 100644
--- a/Part-4/part04-Part04_21.NumberOfStrings/pom.xml
+++ b/Part-4/part04-Part04_21.NumberOfStrings/pom.xml
@@ -17,7 +17,7 @@
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
-            <version>4.12</version>
+            <version>4.13.1</version>
             <scope>test</scope>
         </dependency>
         <dependency>