ugly behaviour with doublespace package in figure environement

[Aurèle Duda]

Strange but not problematic because the use of 'setspace' package, more 
useful, work correctly. When you compile this sample.lytex, the first 
lilypond snippet produce a good output, but not the second. It is caused 
by the doublespace package.
I use lilypond 2.2.5 on cygwin/XP.

Bye!
Aurèle Duda

\documentclass[12pt,a4paper]{book}
\usepackage[francais]{babel}
\usepackage[T1]{fontenc}
\usepackage[ansinew]{inputenc}
\usepackage{doublespace}
\begin{document}
\lilypond[staffsize=12,linewidth=10\cm]{ a a a a a }
\begin{figure}[htbp]
 \centering
 \lilypond[staffsize=12,linewidth=10\cm]{ a a a a a } 
 \caption{this doesn't work}
\end{figure}
\end{document}