diff --git a/_config.yml b/_config.yml
index 1e2e141..368503d 100644
--- a/_config.yml
+++ b/_config.yml
@@ -26,8 +26,8 @@ navbar:
     menu:
         # Home: /
         Archives: /archives
-        サークル参加😺: https://techbookfest.org/event/tbf12#requirements
-        技術書典12（オンライン：1/22-1/30）: https://techbookfest.org/event/tbf12
+        サークル参加😺: https://techbookfest.org/event/tbf13#requirements
+        技術書典13（オンライン：9/10-9/25、オフライン：9/11）: https://techbookfest.org/event/tbf13
         # Categories: /categories
         # Tags: /tags
         # About: /about
diff --git a/includes/helpers/page.js b/includes/helpers/page.js
index b755e28..a44c37b 100644
--- a/includes/helpers/page.js
+++ b/includes/helpers/page.js
@@ -115,7 +115,7 @@ module.exports = function (hexo) {
         else if (hasThumbnail)
             og_image = getThumbnail(post);
         else
-            og_image = getConfig('article.og_image', '/images/og_image.jpg');
+            og_image = getConfig('article.og_image', '/images/og_image.png');
 
         return this.url_for(og_image);
     });
diff --git a/source/images/og_image.jpg b/source/images/og_image.jpg
deleted file mode 100644
index 0a487d3..0000000
Binary files a/source/images/og_image.jpg and /dev/null differ
diff --git a/source/images/og_image.png b/source/images/og_image.png
new file mode 100644
index 0000000..723ff33
Binary files /dev/null and b/source/images/og_image.png differ