cleveref: \lcnamecref fails to work with theorem names that are not pre-defined

Question

I'm using cleveref with the capitalise option, and I'd like to use the \lcnamecref command to give the name of one of my theorems in the text. But if this is not one of the theorem types pre-defined in cleveref (Lemma, Theorem etc.) then I get an error message. Here's a MWE:

\documentclass{article}
\usepackage{amsthm}
\usepackage[capitalise]{cleveref}

\crefname{mythm}{Mytheorem}{Mytheorems}
\newtheorem{mythm}{Mytheorem}

\begin{document}
\begin{mythm}\label{m}
foo
\end{mythm}
That was a \lcnamecref{m}.
\end{document}

When I compile I get the error message

! Argument of \MakeUppercase has an extra }.

What am I doing wrong?

Answer 1

\lcnamecref will force lowercase for the names defined with \Crefname (the upper-case variant), so you have to use this macro in the preamble.

\documentclass{article}
\usepackage{amsthm}
\usepackage[capitalise]{cleveref}

% \crefname{mythm}{Mytheorem}{Mytheorems}
\Crefname{mythm}{Mytheorem}{Mytheorems}
\newtheorem{mythm}{Mytheorem}

\begin{document}
\begin{mythm}\label{m}
foo
\end{mythm}
That was a \lcnamecref{m}.
\end{document}