diff --git a/app/models/cdao/subject.rb b/app/models/cdao/subject.rb
index 9f47ae1..a170873 100644
--- a/app/models/cdao/subject.rb
+++ b/app/models/cdao/subject.rb
@@ -8,7 +8,7 @@ class Cdao::Subject < Cdao::Base
 
   has_ancestry
 
-  has_many :library_subjects, dependent: :restrict_with_error
+  has_many :library_subjects, dependent: :destroy
   accepts_nested_attributes_for :library_subjects, allow_destroy: true
 
   has_many :libraries, through: :library_subjects