NSTableHeaderView prevents auto layout from resizing scroll view in a split view
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I'm trying to embed my custom view in a scroll view, which in turn is enclosed in a split view.

I can drag the split divider from top to all the way to bottom, except when my custom view provides a header view for the scroll view. This prevents me dragging the divider over the custom view to hide it partially within the scroll view. It looks like that with header view, my custom view becomes the minimum size what the scroll view can be.

If I return nil from the headerView property of my custom view the user can move the divider freely to any position. 

I can reproduce this every time by following these steps:

1. Create a new Cocoa Application project
2. Create TestView class with headerView property which returns a NSTableHeaderView instance.
3. Edit MainMenu.xib and add a split view
4. Add custom view and make it TestView
5. Choose Editor -> Embed in -> Scroll view
6. Run the project

(No constraints or other Interface Builder menus touched)

Here's a pic, which I couldn't embed as a new user: http://imgur.com/WQe7F

Code of TestView:

    @implementation TestView

    - (NSTableHeaderView *)headerView
    {
        static NSTableHeaderView *header = nil;
        
        if (!header) {
            header = [[NSTableHeaderView alloc] initWithFrame:NSMakeRect(0.0, 0.0, 100.0, 17.0)];
        }
                      
        return header;
    }

    @end

What am I doing wrong, or how can I circumvent this so that the user can drag the divider freely?