NSMetadataQuery sorting by update date is not working

Question

I am trying to sort the results of a NSMetadataQuery by update date but it is not working.

Here is my code:

self.query = [[NSMetadataQuery new] autorelease];
[self.query setSearchScopes:@[NSMetadataQueryUbiquitousDataScope]];
NSSortDescriptor *sortKeys=[[[NSSortDescriptor alloc] initWithKey:NSMetadataItemFSContentChangeDateKey ascending:YES] autorelease];
[self.query setSortDescriptors:@[sortKeys]];
[self.query setPredicate:[NSPredicate predicateWithFormat:[NSString stringWithFormat:@"%%K LIKE '*.%@'", EXTENSION], NSMetadataItemFSNameKey]];
[self.query enableUpdates];
[self.query startQuery]; 

But the results I receive are definitely not sorted by update date... Any suggestions?