diff --git a/prelude.sty b/prelude.sty
index 85fd7a943..96f504af1 100644
--- a/prelude.sty
+++ b/prelude.sty
@@ -59,6 +59,7 @@
 \usepackage{sourcecodepro}
 \usepackage{cleveref}
 \usepackage{etoolbox}
+\usepackage{csquotes}
 
 \titleformat{\paragraph}
 {\normalfont\normalsize\bfseries}{\theparagraph}{1em}{}
@@ -332,13 +333,17 @@
 
 \DeclareOption{en}{
   \babelfont[chinese]{rm}{Noto Serif CJK SC}
-  \newtheorem{axiom}{Axiom}[section]
+  \theoremstyle{plain}
   \newtheorem{theorem}{Theorem}[section]
   \newtheorem{lemma}[theorem]{Lemma}
   \newtheorem{proposition}[theorem]{Proposition}
   \newtheorem{corollary}[theorem]{Corollary}
+
+  \theoremstyle{definition}
+  \newtheorem{axiom}{Axiom}[section]
   \newtheorem{definition}{Definition}[section]
   \newtheorem{example}{Example}[section]
+
   \AtEndEnvironment{Exercise}{
     \par \rightline{\AnswerListName: \cpageref{\ExerciseLabel-Answer}}}
 }