diff --git a/db/migrate/20180910155506_add_uniqueness_of_order_id_to_spree_shipments.rb b/db/migrate/20180910155506_add_uniqueness_of_order_id_to_spree_shipments.rb
new file mode 100644
index 0000000000..21ad966ad4
--- /dev/null
+++ b/db/migrate/20180910155506_add_uniqueness_of_order_id_to_spree_shipments.rb
@@ -0,0 +1,6 @@
+class AddUniquenessOfOrderIdToSpreeShipments < ActiveRecord::Migration
+  def change
+    remove_index :spree_shipments, :order_id
+    add_index :spree_shipments, :order_id, unique: true
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 1d7f167724..007691a87c 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -11,7 +11,7 @@
 #
 # It's strongly recommended to check this file into your version control system.
 
-ActiveRecord::Schema.define(:version => 20180812214434) do
+ActiveRecord::Schema.define(:version => 20180910155506) do
 
   create_table "account_invoices", :force => true do |t|
     t.integer  "user_id",    :null => false
@@ -876,7 +876,7 @@ ActiveRecord::Schema.define(:version => 20180812214434) do
   end
 
   add_index "spree_shipments", ["number"], :name => "index_shipments_on_number"
-  add_index "spree_shipments", ["order_id"], :name => "index_spree_shipments_on_order_id"
+  add_index "spree_shipments", ["order_id"], :name => "index_spree_shipments_on_order_id", :unique => true
 
   create_table "spree_shipping_categories", :force => true do |t|
     t.string   "name"