Chemmacros reactions environment compile error

Question

The package chemmacros will throw the following error when I try to use the reaction or reactions environments. It does not happen when I use the starred variants. I am using MacTeX-2017 and am (fairly) confident everything is up to date.

./main.tex:11: Undefined 

control sequence.
<argument> \l__chemmacros_hyperref_bool 

l.11     \end
             {reaction}
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.

MWE. I compile with latexmk on Atom but the same error occurs in TeXShop and using pdfLatex.

\documentclass{article}

\usepackage[compatibility = 5.8a]{chemmacros}
\chemsetup{
    modules=reactions,
}

\begin{document}
Before
    \begin{reaction}
        H2O -> CO2
    \end{reaction}
Afterwards
\end{document}

I also noticed that a pdf file is made, and everything seems to be in there. However, there is a Greek letter after the equation number that the chemmacros package does not indicate should be there (p43).