Indefinite hang-up with round-mode=figures and naked exponentials

[gustaphe]

\documentclass{standalone}
\usepackage[%
    round-mode=figures % Line x
]{siunitx}
\begin{document}
\num{e5} (This is a way to write \(10^5\))
%\num{1e5} (This works, but includes a significand)
\end{document}

This MWE hangs indefinitely when compiled. Commenting out line x makes it work as expected.

It seems like siunitx is trying to find the first n digits of an empty significand. My siunitx version is 3.2.2, from texlive on Arch Linux.