diff --git a/lib/acts_as_follower/follower_lib.rb b/lib/acts_as_follower/follower_lib.rb
index fa40023..b4a26d5 100644
--- a/lib/acts_as_follower/follower_lib.rb
+++ b/lib/acts_as_follower/follower_lib.rb
@@ -33,7 +33,7 @@ def apply_options_to_scope(scope, options = {})
     end
 
     def parent_classes
-      return DEFAULT_PARENTS unless ActsAsFollower.custom_parent_classes
+      return DEFAULT_PARENTS unless ActsAsFollower.custom_parent_classes.present?
 
       ActiveSupport::Deprecation.warn("Setting custom parent classes is deprecated and will be removed in future versions.")
       ActsAsFollower.custom_parent_classes + DEFAULT_PARENTS