Issue with titlesec page styles and appendix in book class

Issue with titlesec page styles and appendix in book class

I'm using titlesec to set my page style in a book class. If I include an appendix, the header corresponding to the first chapter is "Appendix 1" instead of "Chapter 1".
\documentclass{book}

\usepackage[pagestyles]{titlesec} 
\newpagestyle{main}[\scshape]{%
  \sethead
  [\thepage][][\chaptertitlename\space\thechapter. \chaptertitle]
  {\ifthesection{\thesection\space\,\sectiontitle}
  {\chaptertitlename\space\thechapter. \chaptertitle}}{}{\thepage}
}
\pagestyle{main}
\usepackage{lipsum}

\begin{document}

\chapter{Foo}
\lipsum

\appendix
\chapter{Bar}
\lipsum

\end{document}