How do I use pfquery in parse.com filtering on a boolean field in ios?

doing a query in an ios/objective c app against a Parse.com datasource how do I construct my PFQuery to filter on a boolean column?

I have something like this;

PFQuery *query = [PFQuery queryWithClassName:@"MyClass"];
[query whereKey:@"MyBoolCol" equalTo:TRUE];

How do I construct this please?

Thanks.