Header scrolls to opposite direction

I noticed that when, e.g., a tree view does not fit completely in the viewport and you use the horizontal scroll bar to move columns into the viewport that are currently hidden, the header scrolls to the opposite direction.

This can be reproduced the following way:

1) Open Designer (6.9.1 in my case)

2) In the treeview of the Object Inspector resize the "Object" column so that a horizontal scroll bar appears that with a handle that is roughly half the size of the viewport.

3) Click an drag the handle to the right and observe the header and the rows.