diff --git a/app/models/france_connect_information.rb b/app/models/france_connect_information.rb
index c4deb17a2..bdc6d5d5b 100644
--- a/app/models/france_connect_information.rb
+++ b/app/models/france_connect_information.rb
@@ -18,6 +18,8 @@
 #  user_id                       :integer
 #
 class FranceConnectInformation < ApplicationRecord
+  MERGE_VALIDITY = 15.minutes
+
   belongs_to :user, optional: true
 
   validates :france_connect_particulier_id, presence: true, allow_blank: false, allow_nil: false
@@ -39,4 +41,8 @@ class FranceConnectInformation < ApplicationRecord
     update_attribute('user_id', user.id)
     touch # needed to update updated_at column
   end
+
+  def valid_for_merge?
+    (MERGE_VALIDITY.ago < merge_token_created_at) && user_id.nil?
+  end
 end
diff --git a/spec/models/france_connect_information_spec.rb b/spec/models/france_connect_information_spec.rb
index 150b92fc3..ab321cec5 100644
--- a/spec/models/france_connect_information_spec.rb
+++ b/spec/models/france_connect_information_spec.rb
@@ -19,4 +19,28 @@ describe FranceConnectInformation, type: :model do
       end
     end
   end
+
+  describe '#valid_for_merge?' do
+    let(:fci) { create(:france_connect_information) }
+
+    subject { fci.valid_for_merge? }
+
+    context 'when the merge token is young enough' do
+      before { fci.merge_token_created_at = 1.minute.ago }
+
+      it { is_expected.to be(true) }
+
+      context 'but the fci is already linked to an user' do
+        before { fci.update(user: create(:user)) }
+
+        it { is_expected.to be(false) }
+      end
+    end
+
+    context 'when the merge token is too old' do
+      before { fci.merge_token_created_at = (FranceConnectInformation::MERGE_VALIDITY + 1.minute).ago }
+
+      it { is_expected.to be(false) }
+    end
+  end
 end