diff --git a/lib/graphiti/sideload/polymorphic_belongs_to.rb b/lib/graphiti/sideload/polymorphic_belongs_to.rb
index 141ad5e1..40946a6e 100644
--- a/lib/graphiti/sideload/polymorphic_belongs_to.rb
+++ b/lib/graphiti/sideload/polymorphic_belongs_to.rb
@@ -41,7 +41,7 @@ def ignore?(group_name)
     end
 
     def on(name, &blk)
-      group = Group.new(name)
+      group = Group.new(name.to_sym)
       @groups << group
       group
     end