\documentclass{article}
\usepackage{xkeyval}
\makeatletter
\def\XKV@ch@ckch@ice#1#2#3{%
\def\XKV@tempa{#1}%
\ifx\XKV@tempa\@nnil\let\XKV@tempa\@empty\else
\def\XKV@tempa{\def#1{#2}}%
\fi
\begingroup\edef\x{\endgroup\noexpand\in@{,#2,}}\x{,#3,}
%%% \in@{,#2,}{,#3,} original
\ifin@
\ifXKV@pl
\XKV@addtomacro@n\XKV@tempa\@firstoftwo
\else
\XKV@addtomacro@n\XKV@tempa\@firstofone
\fi
\else
\ifXKV@pl
\XKV@addtomacro@n\XKV@tempa\@secondoftwo