diff --git a/lib/restpack_serializer/serializable.rb b/lib/restpack_serializer/serializable.rb
index f798aba..3d3042c 100644
--- a/lib/restpack_serializer/serializable.rb
+++ b/lib/restpack_serializer/serializable.rb
@@ -67,7 +67,11 @@ def add_links(model, data)
       self.class.associations.each do |association|
         if association.macro == :belongs_to
           data[:links] ||= {}
-          foreign_key_value = model.send(association.foreign_key)
+          foreign_key_value = if association.polymorphic?
+            model.send(association.name).to_param
+          else
+            model.send(association.foreign_key)
+          end
           if foreign_key_value
             data[:links][association.name.to_sym] = foreign_key_value.to_s
           end