Index: Ringtoets/AssemblyTool/test/Ringtoets.AssemblyTool.IO.TestUtil/SerializableAttributeTestHelper.cs
===================================================================
diff -u -rc3a1ccde5d4e1f1950065d16a6eb83f02a9930c6 -ra77ce8324ad774ff960b1292d02a51a867869d7a
--- Ringtoets/AssemblyTool/test/Ringtoets.AssemblyTool.IO.TestUtil/SerializableAttributeTestHelper.cs	(.../SerializableAttributeTestHelper.cs)	(revision c3a1ccde5d4e1f1950065d16a6eb83f02a9930c6)
+++ Ringtoets/AssemblyTool/test/Ringtoets.AssemblyTool.IO.TestUtil/SerializableAttributeTestHelper.cs	(.../SerializableAttributeTestHelper.cs)	(revision a77ce8324ad774ff960b1292d02a51a867869d7a)
@@ -46,9 +46,9 @@
         /// </exception>
         public static void AssertXmlTypeAttribute(Type type, string typeName)
         {
-            var attribute = (XmlTypeAttribute) type.GetCustomAttributes(typeof(XmlTypeAttribute), false).SingleOrDefault();
-            Assert.IsNotNull(attribute);
-            Assert.AreEqual(typeName, attribute.TypeName);
+            var attributes = (XmlTypeAttribute[]) type.GetCustomAttributes(typeof(XmlTypeAttribute), false);
+            Assert.AreEqual(1, attributes.Length);
+            Assert.AreEqual(typeName, attributes.Single().TypeName);
         }
 
         /// <summary>