Follow the coding conventions

activerecord/lib/active_record/scoping/named.rb

@@ -139,7 +139,7 @@ def scope_attributes? # :nodoc:
         #   Article.published.featured.latest_article
         #   Article.featured.titles
         def scope(name, body, &block)
-          unless body.respond_to?:call
+          unless body.respond_to?(:call)
             raise ArgumentError, 'The scope body needs to be callable.'
           end