UIBarButton doesn't restore itself when I set customView to nil

I've got a UIBarButtonItem that refreshes my data, and while the update is in process, I set refreshButton.customView to an instance of UIActivityIndicator, which is displayed fine. However, when data has been updated and I call refreshButton.customView = nil, the initial UIBarButton开发者_运维问答Item is not displayed any more (just a blank space). Anyone knows how can I fix this?