diff --git a/build.gradle b/build.gradle
index 747b2bb2f0..46e010e174 100644
--- a/build.gradle
+++ b/build.gradle
@@ -184,7 +184,7 @@ configure(allprojects) { project ->
 			dependency "org.testng:testng:7.3.0"
 			dependency "org.hamcrest:hamcrest:2.1"
 			dependency "org.awaitility:awaitility:3.1.6"
-			dependency "org.assertj:assertj-core:3.16.1"
+			dependency "org.assertj:assertj-core:3.17.1"
 			dependencySet(group: 'org.xmlunit', version: '2.6.2') {
 				entry 'xmlunit-assertj'
 				entry('xmlunit-matchers') {
diff --git a/spring-oxm/src/main/java/org/springframework/oxm/xstream/XStreamMarshaller.java b/spring-oxm/src/main/java/org/springframework/oxm/xstream/XStreamMarshaller.java
index c96998d531..a992ab8141 100644
--- a/spring-oxm/src/main/java/org/springframework/oxm/xstream/XStreamMarshaller.java
+++ b/spring-oxm/src/main/java/org/springframework/oxm/xstream/XStreamMarshaller.java
@@ -46,7 +46,6 @@ import com.thoughtworks.xstream.converters.SingleValueConverter;
 import com.thoughtworks.xstream.converters.reflection.ReflectionProvider;
 import com.thoughtworks.xstream.core.ClassLoaderReference;
 import com.thoughtworks.xstream.core.DefaultConverterLookup;
-import com.thoughtworks.xstream.core.util.CompositeClassLoader;
 import com.thoughtworks.xstream.io.HierarchicalStreamDriver;
 import com.thoughtworks.xstream.io.HierarchicalStreamReader;
 import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
@@ -186,7 +185,8 @@ public class XStreamMarshaller extends AbstractMarshaller implements BeanClassLo
 	@Nullable
 	private Class<?>[] supportedClasses;
 
-	private ClassLoader beanClassLoader = new CompositeClassLoader();
+	@Nullable
+	private ClassLoader beanClassLoader = ClassUtils.getDefaultClassLoader();
 
 	private final SingletonSupplier<XStream> xstream = SingletonSupplier.of(this::buildXStream);