diff --git a/CHANGELOG.md b/CHANGELOG.md
index d0cfff8e2..e940b96ae 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@
 
 ### Implements
 
+- Update the Markdown syntax to fix highlighting strikethrough.
 - Improve the User Guide contents.
 - [non-AppStore ver.] Update Sparkle from 2.6.2 to 2.6.3.
 
diff --git a/CotEditor/Syntaxes/Markdown.yml b/CotEditor/Syntaxes/Markdown.yml
index b445d521f..0dae1fa4b 100644
--- a/CotEditor/Syntaxes/Markdown.yml
+++ b/CotEditor/Syntaxes/Markdown.yml
@@ -39,7 +39,7 @@ extensions:
 filenames: []
 interpreters: []
 keywords:
-- beginString: (?<!\\)\b~~(?![ \t])((?!\R{2})(?:.|\R))*?(?<![\\\t ])~~
+- beginString: (?<!\\)~~[^ \t~]((?!\R{2})(?:.|\R))*?(?<![\\ ])~~
   description: '[github] strikethrough'
   regularExpression: true
 - beginString: \R[\t ]*\R(?:\- *){3,}$
@@ -71,9 +71,9 @@ kind: general
 metadata:
   author: 1024jp
   distributionURL: https://coteditor.com
-  lastModified: '2024-05-10'
+  lastModified: '2024-06-09'
   license: Same as CotEditor
-  version: 1.4.0
+  version: 1.4.1
 numbers:
 - beginString: (?<!\\)!\[.*?(?<!\\)\](?=\()
   description: img