diff --git a/lib/redmine/wiki_formatting/common_mark/sanitization_filter.rb b/lib/redmine/wiki_formatting/common_mark/sanitization_filter.rb
index 7ee973911..94e4b8f5e 100644
--- a/lib/redmine/wiki_formatting/common_mark/sanitization_filter.rb
+++ b/lib/redmine/wiki_formatting/common_mark/sanitization_filter.rb
@@ -28,7 +28,7 @@ module Redmine
         }.freeze
 
         def allowlist
-          @@allowlist ||= customize_allowlist(super.deep_dup)
+          @allowlist ||= customize_allowlist(super.deep_dup)
         end
 
         private