diff --git a/db/migrate/20220405100354_add_uniq_index_on_attestation_dossier_id.rb b/db/migrate/20220405100354_add_uniq_index_on_attestation_dossier_id.rb
new file mode 100644
index 000000000..21b7c8d09
--- /dev/null
+++ b/db/migrate/20220405100354_add_uniq_index_on_attestation_dossier_id.rb
@@ -0,0 +1,9 @@
+class AddUniqIndexOnAttestationDossierId < ActiveRecord::Migration[6.1]
+  include Database::MigrationHelpers
+  disable_ddl_transaction!
+
+  def up
+    remove_index :attestations, :dossier_id
+    add_concurrent_index :attestations, :dossier_id, unique: true
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 40d9f2ece..11feb6627 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2022_03_23_120846) do
+ActiveRecord::Schema.define(version: 2022_04_05_100354) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -134,7 +134,7 @@ ActiveRecord::Schema.define(version: 2022_03_23_120846) do
     t.integer "dossier_id", null: false
     t.string "title"
     t.datetime "updated_at", null: false
-    t.index ["dossier_id"], name: "index_attestations_on_dossier_id"
+    t.index ["dossier_id"], name: "index_attestations_on_dossier_id", unique: true
   end
 
   create_table "avis", id: :serial, force: :cascade do |t|
diff --git a/spec/models/dossier_spec.rb b/spec/models/dossier_spec.rb
index ce5249bc6..2b8298a50 100644
--- a/spec/models/dossier_spec.rb
+++ b/spec/models/dossier_spec.rb
@@ -1480,12 +1480,10 @@ describe Dossier do
     before do
       create(:dossier, transfer: transfer)
       create(:attestation, dossier: dossier)
-      create(:attestation, dossier: dossier)
     end
 
-    it "can destroy dossier with two attestations" do
+    it "can destroy dossier" do
       expect(dossier.destroy).to be_truthy
-      expect(transfer.reload).not_to be_nil
     end
   end