Spurious spaces in Korean

[Derek61]

Consider

\documentclass{article}
\usepackage{polyglossia}

\setmainlanguage{english}
\setotherlanguages{korean,spanish}

\newfontfamily\koreanfont{Apple SD Gothic Neo}

\begin{document}
AB\textkorean{아스트로}EF

AB\textspanish{CD}EF
\end{document}

\end{document}

Compiling with XeLaTeX yields

It would seem likely that a missing "%" is to blame.