If we cannot find the class with the to_s version of the class name, fall back to using the sti_name of the class which can be different

Author: Kyle d'Oliveira

lib/polymorphic_integer_type/extensions.rb

@@ -31,7 +31,10 @@ def belongs_to(name, scope = nil, **options)
 
           define_method "#{foreign_type}=" do |klass|
             enum = mapping.key(klass.to_s)
-            enum ||= mapping.key(klass.base_class.to_s) if klass.kind_of?(Class) && klass <= ActiveRecord::Base
+            if klass.kind_of?(Class) && klass <= ActiveRecord::Base
+              enum ||= mapping.key(klass.base_class.to_s)
+              enum ||= mapping.key(klass.base_class.sti_name)
+            end
             enum ||= klass if klass != NilClass
             super(enum)
           end