UIPopoverPresentationController displaying popover as full screen

I am trying to use UIPopoverPresentationController to display a popover that doesn't take up the whole screen. I've followed many different tutorials with no luck.

Here is my code. It correctly instantiates the ViewController, but it takes up the entire screen instead of just a smaller screen as I defined in preferredContentSize.

func showPopover() {
    let vc = self.storyboard?.instantiateViewControllerWithIdentifier("PopupTimePickerViewController") as PopupTimePickerViewController
    vc.modalPresentationStyle = .Popover
    vc.preferredContentSize = CGSizeMake(200, 100)

    if let presentationController = vc.popoverPresentationController {
        presentationController.delegate = self
        presentationController.permittedArrowDirections = .Up
        presentationController.sourceView = self.view
        presentationController.sourceRect = CGRectMake(0, 0, 50, 50)

        self.presentViewController(vc, animated: true, completion: nil)
    }
}

Update 9/27/16 with correct answer

func adaptivePresentationStyle(for controller: UIPresentationController, traitCollection: UITraitCollection) -> UIModalPresentationStyle {
    return .none
}

In iPhone, you should add the following in order to present a popover.

func adaptivePresentationStyleForPresentationController(controller: UIPresentationController!) -> UIModalPresentationStyle {
    // Return no adaptive presentation style, use default presentation behaviour
    return .None
}