\ifx\lst@framelshape\@empty \let\lst@frameL\@empty \fi
\ifx\lst@framershape\@empty \let\lst@frameR\@empty \fi
\def\lst@framevrule{\vrule\@width\lst@framerulewidth\relax}%
\ifx\lst@framelshape\@empty \let\lst@frameL\@empty \fi
\ifx\lst@framershape\@empty \let\lst@frameR\@empty \fi
\def\lst@framevrule{\vrule\@width\lst@framerulewidth\relax}%