页眉中的编号索引

Question

使用文档类“scrbook”中的值“index=numbered”，我将本例中的章节标题从“MyIndex”更改为“2 MyIndex”。在页眉中仍然打印“MyIndex”而不是“2 MyIndex”。除非 markboth 命令在这里不起作用，否则我该如何在使用 Koma Script 时修复此问题。

\documentclass[
    10pt,
    twoside,
    toc=listofnumbered,
    listof=flat,
    headinclude,
    footinclude,
    index=numbered,
    usegeometry
]{scrbook}
\usepackage[T1]{fontenc}
\usepackage[ngerman]{babel}
\usepackage{makeidx}

\usepackage[headsepline]{scrlayer-scrpage}
\pagestyle{scrheadings}
\ohead{\headmark}
\automark[section]{chapter}
\setkomafont{pagehead}{\upshape\sffamily\small}
\addtokomafont{pagenumber}{\sffamily\small}

\addto\captionsngerman{
    \def\indexname{MyIndex}%
    }
\makeindex
\makeatother

\begin{document}
\chapter{MyFirstPage}
Foo \index{foo}

Moo \index{moo}
\printindex%\markboth{Huhu}{Huhu} %this does not work here
\end{document}