UITextView not fitting to content

I am using this code to create a UITextView that is suppose to fit within a UIView container:

// Make the cellTextView.
let cellTextView = UITextView()
cellTextView.backgroundColor = UIColor.clearColor()
cellTextView.translatesAutoresizingMaskIntoConstraints = false
cellTextView.scrollEnabled = false
superview.addSubview(cellTextView)

// Constrain the cellTextView.
cellTextView.topAnchor.constraintEqualToAnchor(superview.topAnchor, constant: 8).active = true
cellTextView.bottomAnchor.constraintEqualToAnchor(superview.bottomAnchor, constant: -8).active = true
cellTextView.leadingAnchor.constraintEqualToAnchor(superview.leadingAnchor, constant: 8).active = true
cellTextView.trailingAnchor.constraintEqualToAnchor(superview.trailingAnchor, constant: -8).active = true

But it is producing this result:

This is what it should look like:

I have tried a lot of different things, but nothing fixes it. Any suggestions will be greatly appreciated.