Grid layout not working

[vrilcode]

I wanted to use grid layout with book class. Chapter or section titles do not fit in grid spacing, which should not be a problem as usually only normal paragraphs have to be on the grid. All other elements should probably start on a grid line, but don't have to (and can't) end on grid. I couldn't achieve this behavior by switching grid typesetting on for the whole document. So I tried to switch grid typesetting on only before sectioning elements and switch it off afterwards. Doesn't seem to be a solution, but more an attempt. But that doesn't work either. Please see my minimal example below (output PDF attached).
Am I doing something wrong? Is there a solution for my problem?

\begin[papersize=a5,class=book]{document}
\use[module=packages.lorem]
\use[module=packages.grid]

\chapter{This is a very lony chapter title, which doesn't fit in one line anymore}
\grid[spacing=15pt]\grid:debug\lorem\no-grid
\section{This is a very long section title, which doesn't fit in one line anymore}
\grid[spacing=15pt]\grid:debug\lorem[words=1500]\no-grid

\end{document}

test_book.pdf