\DeclareSIPrefix results in printing of "powers-ten" instead of "symbol"

[FloDX]

In version 2, I faced no problem when defining a new SI prefix like in the following example:

\documentclass {article}
\usepackage{siunitx}
\DeclareSIPrefix{\trillion}{\text{trillion\,}}{12}
\DeclareSIUnit{\dollar}{\text{\$}}

\begin{document}
\SI{3}{\trillion\dollar}
\end{document}

which leads to the desired output of "3 trillion $".

Using version 3 of siunitx, it prints "3 12$", instead.

Thanks a lot for any help on this issue.