diff --git a/app/models/post.rb b/app/models/post.rb
index bacfe73aa..6f81f3427 100644
--- a/app/models/post.rb
+++ b/app/models/post.rb
@@ -188,7 +188,7 @@ class Post < ApplicationRecord
     end
 
     def is_image?
-      file_ext =~ /jpg|gif|png|webp|avif/i
+      file_ext.in?(%w[jpg gif png webp avif])
     end
 
     def is_flash?