diff --git a/src/test/org/openscience/cdk/tools/diff/tree/IntegerDifferenceTest.java b/src/test/org/openscience/cdk/tools/diff/tree/IntegerDifferenceTest.java
index <HASH>..<HASH> 100644
--- a/src/test/org/openscience/cdk/tools/diff/tree/IntegerDifferenceTest.java
+++ b/src/test/org/openscience/cdk/tools/diff/tree/IntegerDifferenceTest.java
@@ -58,4 +58,11 @@ public class IntegerDifferenceTest extends CDKTestCase {
         Assert.assertNotNull(diffString);
         assertOneLiner(diffString);
     }
+
+    @Test public void testRefs() {
+        Integer x = new Integer(1);
+        Integer y = new Integer(1);
+        IDifference diff = IntegerDifference.construct("foo", x, y);
+        Assert.assertNull(diff);
+    }
 }
Added a test to ensure that Integer objects are compared by value rather than reference