diff --git a/approvaltests/pom.xml b/approvaltests/pom.xml
index f1f0b6b6..5c8ec9c4 100644
--- a/approvaltests/pom.xml
+++ b/approvaltests/pom.xml
@@ -34,7 +34,7 @@
         <dependency>
             <groupId>com.thoughtworks.xstream</groupId>
             <artifactId>xstream</artifactId>
-            <version>1.4.20</version>
+            <version>1.4.21</version>
             <optional>true</optional>
         </dependency>
         <dependency>