diff --git a/app/models/metadata_template.rb b/app/models/metadata_template.rb
index e210fd2c..97a631c1 100644
--- a/app/models/metadata_template.rb
+++ b/app/models/metadata_template.rb
@@ -198,7 +198,7 @@ MetadataTemplate = Struct.new(:site, :document, :name, :label, :type,
 
   def allowed_attributes
     @allowed_attributes ||= %w[style href src alt controls data-align data-multimedia data-multimedia-inner id
-                               name rel target referrerpolicy].freeze
+                               name rel target referrerpolicy class].freeze
   end
 
   def allowed_tags