multline and mdframed bug [closed]

Question

I do not think this bug has been reported anywhere. At least, I could not find such a report. Below is a piece of code to see the problem. The frame in the right margin is improperly calculated.

\documentclass[10pt,fleqn]{book}
\usepackage{xcolor}
\usepackage{amsmath,amsthm}
\usepackage[framemethod=tikz]{mdframed}
\newmdtheoremenv[backgroundcolor=red!10]{theorem}{Theorem}
\begin{document}
\begin{theorem}text\begin{multline}text\end{multline}text\end{theorem}
\begin{theorem}text\begin{equation}text\end{equation}text\end{theorem}
\end{document}