UIScrollView height while adding content programmatically in UIStackView

I am trying to make a view containing an UIScrollView. This UIScrollView contains 3 UIViews. The last one contains another UIStackView I wanted to fill at runtime.

Here an image of the storyboard :

But when I add content at runtime in the second UIStackView, the ScrollView's height remains the same.

The second UIStackView is defined as the first one with:

• Axis : vertical
• Alignment : Fill
• Distribution : Equal Spacing

Then I use :

mStackView.addArrangedSubview(matProgress)

The result below :

What's the way to have the bottom view and the ScrollView stretch to fit the content.