Segue not triggering with custom Table Cell

I'm struggling with segueing from one View Controller to another using a custom Table View Cell. The issue that occurs is that sometimes segues aren't triggered just by tapping the cell, but I have to tap twice.

For better understanding I've put a video on youtube.

https://youtu.be/cJI6jRc5vuA

As you can see in the video each time I tap a cell, I print out "Selected". However, some times when I tap the cell, the log prints out "Selected" but the segue isn't triggered before I tap anywhere in the app again.

Here's the code I use in this video. The code isn't that interesting though, since most is done in the storyboard.

First View Controller

    func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
   
        return 100.0
    }

    func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
   
        return 2
    }

    func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
   
        var cell = tableView.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath) as! CustomCell
   
        cell.firstLabel.text = "I'm a Custom Cell"
   
        return cell
    }

        func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
        println("Selected")
    }

Custom Table View Cell

class CustomCell: UITableViewCell {
  
    @IBOutlet var firstLabel: UILabel!
}

I'm using Xcode 6.4 and I've tested the app on several iOS devices with the same result.

Any help would be very much appreciated.
Thank you,
HE.