Can't find mapping model for migration - UIManagedDocument Core Data Migration

I have two versions of my model Model001.xcdatamodel and Model002.xcdatamodel. These two are in the Model.xcdatamodeld bundle. I also have a Model001to002.xcmappingmodel which is not part of the Model.xcdatamodeld. I checked: both the xcmappingmodel and the xcdatamodeld get copied into the .app bundle.

My managed object context is initialized like this:

    NSURL *documentModel = [bundle URLForResource:@"Model" 
                                     withExtension:@"momd"]; managedObjectModel = [[NSManagedObjectModel alloc]
    initWithContentsOfURL:documentModel]; return managedObjectModel;

I also set these properties on my overridden initWithFileURL: in my UIManagedObject subclass.

    NSMutableDictionary *options = [NSMutableDictionary dictionaryWithDictionary:self.persistentStoreOptions];
    [options setObject:@YES forKey:NSMigratePersistentStoresAutomaticallyOption];
    [options setObject:@YES forKey:NSInferMappingModelAutomaticallyOption];
    self.persistentStoreOptions = [options copy];

But when I try to open a documet, I get the following error: Can't find mapping model for migration

-- UPDATE --

Even if I do a manual migration

     [NSMappingModel mappingModelFromBundles:@[[NSBundle mainBundle]]
                              forSourceModel:sourceObjectModel
                            destinationModel:self.managedObjectModel];

this returns nil. Although I double checked that the Model001to002.cdm is in the app bundle. It has to be in the app bundle right?