kvmatrix inserts [b] in each cell

In the past, I had no problems with code similar to the one below:

documentclass{article}
usepackage{kvmap}
begin{document}
begin{kvmap}
begin{kvmatrix}{B,A}
1 & 
& 1
end{kvmatrix}
end{kvmap}
end{document}

But recently, the same code now shows the text [b] added to each cell:

What can I do to remove this unwanted [b]? I’m using pdfLaTeX, MiKTeX 2.9, and the May 6, 2020 version of kvmap (0.3.4).