Example numbers in right-to-left environment with ExPex

I was delighted to see that expex does interlinear text in right-to-left languages nearly perfectly. One issue, however, is that the example number is placed in the right margin instead of aligned to the text in the page. I am currently working around this by placing the entire gloss line in a minipage (the commented lines below), but I would like to avoid this if I can so that lines of the gloss can break across pages.

\documentclass{book}
\usepackage[a4paper,left=2cm,right=2cm,top=2cm,bottom=2cm]{geometry}
\usepackage{expex,polyglossia,lipsum}
\setdefaultlanguage[variant=american]{english}
\setotherlanguage[numerals=eastern]{farsi}
\newfontfamily\englishfont[Mapping=tex-text]{Times New Roman}
\newfontfamily\farsifont[Script=arab,Scale=MatchLowercase]{Scheherazade}
\begin{document}
\lipsum[1]
%\begin{minipage}{155mm}
\begin{farsi}
\ex[everyglb=\englishfont] \begingl
\gla این مثال من است// 
\glb in masale man ast //
\glb this example me is //
\endgl\xe
\end{farsi}
%\end{minipage}
\end{document}