CPScrollView resizes on first scroll

When I create a basic scroll view with code like this:

var scrollView = [[CPScrollView alloc] initWithFrame:CPRectMake(0, 0, 500, 150)];
var docView = [[CPView alloc] initWithFrame:CPRectMake(0, 0, 500, 300)];
[scrollView setDocumentView:docView];
[scrollView setHasHorizontalScroller:NO];
[[self contentView] addSubview:scrollView];

the CPScrollView adjusts it's height when I start scrolling. The change in height appears to be equal to the size of the horizontal scroller.

If I swap the setDocumentView: and setHasHorizontalScroller: call however, it works as expected without resizing.

var scrollView = [[CPScrollView alloc] initWithFrame:CPRectMake(0, 0, 500, 150)];
var docView = [[CPView alloc] initWithFrame:CPRectMake(0, 0, 500, 300)];
[scrollView setHasHorizontalScroller:NO];
[scrollView setDocumentView:docView];
[[self contentView] addSubview:scrollView];