Increasing/decreasing text size in Assistant broken

Cant change size of text when reading documentation.
Using zoom in/out toolbar buttons only changes text size of titles and not rest of text, and default text size is much smaller than in Assistant 5.5.1 (which I reverted using with added Qt 5.6 documentation)

I attached 2 screen shots containing Assistant 5.5.1 below 5.6.0 one at default zoom level and second one with 5x zoom in clicked