diff --git a/Gemfile b/Gemfile
index 1650f8fc0..82e6dbf40 100644
--- a/Gemfile
+++ b/Gemfile
@@ -19,7 +19,7 @@ gem 'activeadmin-xls', git: 'https://github.com/shanser/activeadmin-xls',
                        branch: 'autoload'
 gem 'acts_as_list'
 gem 'addressable'
-gem 'ancestry', '< 4.3'
+gem 'ancestry', '~> 4.3'
 gem 'auto_strip_attributes', '~> 2.6'
 gem 'bootsnap', '>= 1.1.0', require: false
 gem 'bootstrap', '~> 4.3', '>= 4.3.1'
diff --git a/Gemfile.lock b/Gemfile.lock
index 71ebd9b36..d98eafdcf 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -111,7 +111,7 @@ GEM
     addressable (2.8.4)
       public_suffix (>= 2.0.2, < 6.0)
     afm (0.2.2)
-    ancestry (4.2.0)
+    ancestry (4.3.3)
       activerecord (>= 5.2.6)
     arbre (1.5.0)
       activesupport (>= 3.0.0, < 7.1)
@@ -555,7 +555,7 @@ DEPENDENCIES
   activeadmin_reorderable
   acts_as_list
   addressable
-  ancestry (< 4.3)
+  ancestry (~> 4.3)
   auto_strip_attributes (~> 2.6)
   aws-sdk-s3
   bootsnap (>= 1.1.0)
diff --git a/app/models/structure.rb b/app/models/structure.rb
index 20abdce21..f82458c84 100644
--- a/app/models/structure.rb
+++ b/app/models/structure.rb
@@ -1,8 +1,7 @@
 # frozen_string_literal: true
 
 class Structure < ApplicationRecord
-  REGEX_UUID = /\A[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}/i.freeze
-  has_ancestry(primary_key_format: REGEX_UUID)
+  has_ancestry
   acts_as_paranoid
 
   alias structure_referente parent
diff --git a/config/initializers/ancestry.rb b/config/initializers/ancestry.rb
new file mode 100644
index 000000000..bfa06fdcb
--- /dev/null
+++ b/config/initializers/ancestry.rb
@@ -0,0 +1,2 @@
+Ancestry.default_primary_key_format = /[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}/i
+Ancestry.default_ancestry_format = :materialized_path2
diff --git a/db/migrate/20230515100936_change_colonne_collation_ancestry_pour_structures.rb b/db/migrate/20230515100936_change_colonne_collation_ancestry_pour_structures.rb
new file mode 100644
index 000000000..00ff886ae
--- /dev/null
+++ b/db/migrate/20230515100936_change_colonne_collation_ancestry_pour_structures.rb
@@ -0,0 +1,14 @@
+class ChangeColonneCollationAncestryPourStructures < ActiveRecord::Migration[7.0]
+  class Structure < ApplicationRecord
+    has_ancestry
+  end
+  def change
+    model = Structure
+    # set all child nodes
+    model.where.not(model.arel_table[model.ancestry_column].eq(nil)).update_all("#{model.ancestry_column} = CONCAT('#{model.ancestry_delimiter}', #{model.ancestry_column}, '#{model.ancestry_delimiter}')")
+    # set all root nodes
+    model.where(model.arel_table[model.ancestry_column].eq(nil)).update_all("#{model.ancestry_column} = '#{model.ancestry_root}'")
+
+    change_column :structures, :ancestry, :string, collation: 'C', null: false
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 1e45f9943..c633b2002 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[7.0].define(version: 2023_04_19_084251) do
+ActiveRecord::Schema[7.0].define(version: 2023_05_15_100936) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pgcrypto"
   enable_extension "plpgsql"
@@ -357,7 +357,7 @@
     t.datetime "anonymise_le", precision: nil
     t.string "type"
     t.datetime "deleted_at"
-    t.string "ancestry"
+    t.string "ancestry", null: false, collation: "C"
     t.index ["ancestry"], name: "index_structures_on_ancestry"
     t.index ["deleted_at"], name: "index_structures_on_deleted_at"
     t.index ["latitude", "longitude"], name: "index_structures_on_latitude_and_longitude"
diff --git a/docs/erd.png b/docs/erd.png
index 42295ce64..e709935d6 100644
Binary files a/docs/erd.png and b/docs/erd.png differ
diff --git a/spec/models/structure_spec.rb b/spec/models/structure_spec.rb
index 0664f4b64..97878a567 100644
--- a/spec/models/structure_spec.rb
+++ b/spec/models/structure_spec.rb
@@ -8,9 +8,9 @@
   it { is_expected.to validate_presence_of(:nom) }
   it { is_expected.to validate_uniqueness_of(:nom).scoped_to(:code_postal).case_insensitive }
 
-  describe 'REGEX_UUID' do
-    it { expect('uuid invalide').not_to match(Structure::REGEX_UUID) }
-    it { expect(SecureRandom.uuid).to match(Structure::REGEX_UUID) }
+  describe 'Ancestry primary key format' do
+    it { expect('uuid invalide').not_to match(Ancestry.default_primary_key_format) }
+    it { expect(SecureRandom.uuid).to match(Ancestry.default_primary_key_format) }
   end
 
   def mock_geo_api(departement, code_region, region)