[Tex/LaTex] Strange character when using listings package

Question

I'm seeing an odd character like a very flat U, where there should be a space, with the listings package. See example below. Does anyone have any idea why this is happening, or how to get rid or work around it?

\documentclass{standalone}
\usepackage{underscore}
\usepackage{listings}
\usepackage[usenames,dvipsnames, rgb, svgnames, x11names]{xcolor}
% Text layout
\topmargin 0.0cm
\oddsidemargin 0.5cm
\evensidemargin 0.5cm
\textwidth 16cm
\textheight 21cm 
\lstnewenvironment{cmd}[1][]{%
  \lstset{language=sh, backgroundcolor=\color{LightSteelBlue1}, #1}}
{}

\begin{document}
\begin{cmd}
[affy6]
[...]
    [[hapmap]]
    phenofiles = "data/Hapmap6.0/Pheno/hapmappheno_909.csv",
    genofile = "/data/snppy/Hapmap6.0/Geno/birdseed-v2.calls.txt"
    anno_filter = "chromosome = 5"
    idlink_filter = "studyid = 'CEU'"
    some_other_stuff = "foo = bar"
\end{cmd}
\end{document}

Answer 1

By default, listings shows spaces as a "squat-u" as part of strings (between quotes). Add the option showstringspaces=false to your list of \lstset options to remove this.