diff --git a/app/models/custom_emoji.rb b/app/models/custom_emoji.rb
index 304805659..7d6a09108 100644
--- a/app/models/custom_emoji.rb
+++ b/app/models/custom_emoji.rb
@@ -25,7 +25,7 @@ class CustomEmoji < ApplicationRecord
 
   LIMIT = 256.kilobytes
 
-  SHORTCODE_RE_FRAGMENT = '[a-zA-Z0-9_]{2,}'
+  SHORTCODE_RE_FRAGMENT = '(([[:alnum:]])|_){2,}'
 
   SCAN_RE = /(?<=[^[:alnum:]:]|\n|^)
     :(#{SHORTCODE_RE_FRAGMENT}):