Thmtools declaredtheoremstyle 使用导致未定义的错误

Question

当使用thmtools定义我自己的定理风格时如下：

\documentclass{book}

\usepackage{amsthm}
\usepackage{mdframed}
\usepackage{thmtools}


\definecolor{thmBgColor}{RGB}{250,250,250}
\definecolor{thmLnColor}{RGB}{200,200,200}
\definecolor{davysgrey}{rgb}{0.33, 0.33, 0.33}

\declaretheoremstyle[
    headfont=\color{davysgrey}\sffamily\bfseries\lsstyle,
    within=chapter,  
    headpunct={},
    postheadspace=2mm, 
    notefont=\color{davysgrey}\mdseries, 
    notebraces = {\quad}{},
    spaceabove = 8pt,
    spacebelow = 16pt,
    bodyfont=\color{black}\normalfont\itshape,
    mdframed={
        linecolor=thmLnColor,
        backgroundcolor=thmBgColor,
        linewidth=1pt,
        topline=true,
        bottomline=true,
        rightline=false,
        leftline=false,
        outerlinewidth=2pt,
        roundcorner=0pt,
        innertopmargin=4pt,
        innerbottommargin=4pt,
        innerrightmargin=3pt,
        innerleftmargin=3pt,
        skipabove=\topskip,
        skipbelow=\topskip,
        nobreak=true} 
    ]{mydefstyle}

\declaretheorem[
    style=mydefstyle,
    name=Definition,
    numberwithin=chapter
]{mydef}



\begin{document}

\begin{mydef}[this is my title]
content
\end{mydef}


\end{document}

使用 pdflatex 时我在日志中收到此错误：

Package mdframed Info: mdframed works in twoside mode on input line 51.
Package mdframed Info: mdframed detected package amsthm 
 changed the theorem header of amsthm
(mdframed)              on input line 51.
! Undefined control sequence.
<inserted text> ...y}\sffamily \bfseries \lsstyle 

l.51 \begin{mydef}[this is my title]

The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.

精度：

• 错误出现在书籍和文章文档类中
• 尽管出现错误，但文档仍生成

我怎样才能避免这个错误？

Answer 1

正如@troy 指出的那样，添加 microtype 包可以解决问题。