- don't check the class method, but check that the instance method is…

… defined.

- we don't actually need the instance variable.

lib/declarative_authorization/rails_legacy.rb

@@ -13,11 +13,10 @@ def deep_merge(other_hash)
   end
 end
 
-unless String.respond_to?(:html_safe)
+unless String.instance_methods.include?(:html_safe)
   class String
     def html_safe
-      @_rails_html_safe = true
       self
     end
   end
-end
+end