iPhone Core Data "Automatic Lightweight Migration"

I am attempting to update an app that implements a core data store. I am adding an attribute to one of the entities.

I added the following code to my delegate class:

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {

    if (persistentStoreCoordinator != nil) {
        return persistentStoreCoordinator;
    }

    NSURL *storeUrl = [NSURL fileURLWithPath: [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"Shoppee.sqlite"]];

    NSError *error = nil;
    persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];

    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                             [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
                             [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];

    if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:options error:&error]) {
        NSLog(@"Error: %@",error);
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }    

    return persistentStoreCoordinator;
}

This was from the following URL: Doc

I get the following error when executing the code:

2009-12-01 20:04:22.877

Shoppee[25633:207] Error: Error

Domain=NSCocoaErrorDomain Code=134130

UserInfo=0x1624d20 "Operation could not be completed. (Cocoa error 134130.)" 2009-12-01 20:04:22.879 Shoppee[25633:207] Unresolved error Error Domain=NSCocoaErrorDomain Code=134130 UserInfo=0x1624d20 "Operation could not be completed. (Cocoa error 134130.)", { URL = file://localhost/Users/Eric/Library/Application%20Support/iPhone%20Simulator/User/Applications/A8A8FB73-9AB9-4EB7-8F83-82F5B4467AF1/Documents/MyApp.sqlite; metadata = { NSPersistenceFrameworkVersion = 241; NSStoreModelVersionHashes = { Item = <869d4b20 088e5c44 5c345006 87d245cd 67ab9bc4 14cadf45 180251e9 f741a98f>; Store = <47c250f4 895e6fd1 5033ab42 22d2d493 7819ba75 3c0acffc 2dc54515 8deeed7a>; }; NSStoreModelVersionHashesVersion = 3; NSStoreModelVersionIdentifiers = ( ); NSStoreType = SQLite; NSStoreUUID = "8DC65301-3BC5-42BE-80B8-E44577B8F8E1"; }; reason = "Can't find model for source store"; }

It looks like I somehow need to include the original data model but I am not sure how to do that. Any suggestions?