# Imaginary unit before imaginary part of complex number using siunitx

When using the siunitx package, how can I change the complex number format from 1+2j (or i) to 1+j2? The documentation calls this an "invalid arrangement", but it seems to be common in electrical engineering.

\documentclass{article}
\usepackage{siunitx}
\sisetup{output-complex-root=\ensuremath{j}}
\begin{document}
Default output: \num{1+j2}

Desired output: $$1+\mathrm{j}2$$
\end{document}


 \sisetup{output-complex-root=\ensuremath{j},