Index: src/NHibernate/Type/TypeFactory.cs
===================================================================
--- src/NHibernate/Type/TypeFactory.cs	(revision 4896)
+++ src/NHibernate/Type/TypeFactory.cs	(working copy)
@@ -1127,8 +1127,10 @@
 					object[] targetComponentValues = componentType.GetPropertyValues(target[i], session);
 					object[] componentCopy = ReplaceAssociations(origComponentValues, targetComponentValues, subtypes, session, null, copyCache,
 															foreignKeyDirection);
-					if (!componentType.IsAnyType)
+					
+                    if (!componentType.IsAnyType && target[i] != null)
 						componentType.SetPropertyValues(target[i], componentCopy, session.EntityMode);
+
 					copied[i] = target[i];
 				}
 				else if (!types[i].IsAssociationType)