diff --git a/backend/checkins/test_services.py b/backend/checkins/test_services.py
index 13d71b3..5772138 100644
--- a/backend/checkins/test_services.py
+++ b/backend/checkins/test_services.py
@@ -74,6 +74,17 @@ class CheckInServiceTests(TestCase):
         with self.assertRaises(InvalidToken):
             preview_check_in_token(raw_token, staff_user=self.staff_user)
 
+    def test_preview_rejects_expired_check_in_token(self):
+        reservation = self.create_reservation()
+        _, raw_token = ReservationToken.create_token(
+            reservation=reservation,
+            purpose=ReservationToken.Purpose.CHECK_IN,
+            expires_at=timezone.now() - timedelta(minutes=1),
+        )
+
+        with self.assertRaises(InvalidToken):
+            preview_check_in_token(raw_token, staff_user=self.staff_user)
+
     def test_check_in_succeeds_for_confirmed_reservation(self):
         reservation = self.create_reservation()
         _, raw_token = self.create_check_in_token(reservation)
@@ -158,6 +169,14 @@ class CheckInServiceTests(TestCase):
         with self.assertRaises(InvalidToken):
             confirm_check_in_from_token(raw_token, staff_user=self.staff_user)
 
+    def test_check_in_rejects_used_check_in_token(self):
+        reservation = self.create_reservation()
+        token, raw_token = self.create_check_in_token(reservation)
+        token.mark_used()
+
+        with self.assertRaises(InvalidToken):
+            confirm_check_in_from_token(raw_token, staff_user=self.staff_user)
+
     def create_reservation(self, **overrides):
         data = {
             "performance": self.performance,
diff --git a/infra/docker/compose.yml b/infra/docker/compose.yml
index 0b2ef7f..8945c76 100644
--- a/infra/docker/compose.yml
+++ b/infra/docker/compose.yml
@@ -11,6 +11,7 @@ services:
       DJANGO_DEBUG: ${DJANGO_DEBUG:-false}
       CORS_ALLOWED_ORIGINS: ${CORS_ALLOWED_ORIGINS}
       SITE_BASE_URL: ${SITE_BASE_URL}
+      EMAIL_BACKEND: ${EMAIL_BACKEND}
       TIME_ZONE: ${TIME_ZONE:-Europe/Rome}
       DATABASE_URL: ${DATABASE_URL}
       POSTGRES_DB: ${POSTGRES_DB}