diff --git a/test/src/test/java/org/apache/commons/proxy2/stub/StubBuilderTest.java b/test/src/test/java/org/apache/commons/proxy2/stub/StubBuilderTest.java
index bb64de6..eaf406b 100644
--- a/test/src/test/java/org/apache/commons/proxy2/stub/StubBuilderTest.java
+++ b/test/src/test/java/org/apache/commons/proxy2/stub/StubBuilderTest.java
@@ -114,6 +114,8 @@
             {
                 when(trainee.iterator()).thenAnswer(new ObjectProvider<Iterator<String>>()
                 {
+                    private static final long serialVersionUID = 1L;
+
                     @Override
                     public Iterator<String> getObject()
                     {