diff --git a/lib/hyrax/configuration.rb b/lib/hyrax/configuration.rb
index 5c133eb3e5..2c4e821d17 100644
--- a/lib/hyrax/configuration.rb
+++ b/lib/hyrax/configuration.rb
@@ -683,7 +683,9 @@ def collection_class
     ##
     # @return [Class] the configured collection model class & Hyrax::PcdmCollection
     def collection_classes
-      [collection_model.constantize, Hyrax::PcdmCollection].uniq
+      klasses = [collection_class, Hyrax::PcdmCollection]
+      klasses << ::Collection if defined? ::Collection
+      klasses.uniq
     end
 
     attr_writer :admin_set_model