scrlttr2 & lualatex：缺少数字，视为零

Question

我可以使用 pdflatex 编译以下示例（即使它抱怨缺少 babel 包），但不能使用 TeX Live 2016 中的 lualatex：

\documentclass{scrlttr2}
\begin{document}
\begin{letter}{Name}
    Test
\end{letter}
\end{document}

这会导致以下错误：

Class scrlttr2 Info: used language is `english'.
(scrlttr2)           Supported languages are: `english', `UKenglish',
(scrlttr2)           `british', `american', `USenglish', `australian`,
(scrlttr2)           `canadian', `newzealand',
(scrlttr2)           `german', `ngerman', `austrian', `naustrian',
(scrlttr2)           `swissgerman', `nswissgermsn',
(scrlttr2)           `acadian', `canadien', `francais', `french', 
(scrlttr2)           `dutch', `italian', `spanish', `polish',
(scrlttr2)           `croatian', `finnish', `norsk', `swedish',
(scrlttr2)           `czech'. `slovak'  on input line 4.

! Missing number, treated as zero.
<to be read again> 
p
l.4 \begin{document}

A number should have been here; I inserted `0'.
(If you can't figure out why I needed to see a number,
look up `weird error' in the index to The TeXbook.)

，在 TeXstudio 中显示为“缺失数字，视为零。\begin{document}”。

添加

\documentclass{scrlttr2}
\usepackage{polyglossia}
\setmainlanguage[spelling=new]{german}

没有帮助。