diff --git a/api/app/settings/common.py b/api/app/settings/common.py
index a69aa22b1049..5bc918b87a34 100644
--- a/api/app/settings/common.py
+++ b/api/app/settings/common.py
@@ -805,6 +805,7 @@
     # FE uri to redirect user to from activation email
     "ACTIVATION_URL": "activate/{uid}/{token}",
     # register or activation endpoint will send confirmation email to user
+    "LOGIN_FIELD": "email",
     "SEND_CONFIRMATION_EMAIL": False,
     "SERIALIZERS": {
         "token": "custom_auth.serializers.CustomTokenSerializer",
@@ -1153,8 +1154,9 @@
 LDAP_INSTALLED = importlib.util.find_spec("flagsmith_ldap")
 # The URL of the LDAP server.
 LDAP_AUTH_URL = env.str("LDAP_AUTH_URL", None)
+LDAP_ENABLED = LDAP_INSTALLED and LDAP_AUTH_URL
 
-if LDAP_INSTALLED and LDAP_AUTH_URL:  # pragma: no cover
+if LDAP_ENABLED:  # pragma: no cover
     AUTHENTICATION_BACKENDS.insert(0, "django_python3_ldap.auth.LDAPBackend")
     INSTALLED_APPS.append("flagsmith_ldap")
 
@@ -1227,7 +1229,6 @@
     # The LDAP user username and password used by `sync_ldap_users_and_groups` command
     LDAP_SYNC_USER_USERNAME = env.str("LDAP_SYNC_USER_USERNAME", None)
     LDAP_SYNC_USER_PASSWORD = env.str("LDAP_SYNC_USER_PASSWORD", None)
-    DJOSER["LOGIN_FIELD"] = "username"
 
 SEGMENT_CONDITION_VALUE_LIMIT = env.int("SEGMENT_CONDITION_VALUE_LIMIT", default=1000)
 if not 0 <= SEGMENT_CONDITION_VALUE_LIMIT < 2000000:
diff --git a/api/tests/unit/custom_auth/test_unit_custom_auth_serializer.py b/api/tests/unit/custom_auth/test_unit_custom_auth_serializer.py
index 010a861f30ab..a61eca619fbc 100644
--- a/api/tests/unit/custom_auth/test_unit_custom_auth_serializer.py
+++ b/api/tests/unit/custom_auth/test_unit_custom_auth_serializer.py
@@ -1,5 +1,9 @@
+import typing
+
 import pytest
+from django.contrib.auth.models import AbstractUser
 from django.test import RequestFactory
+from djoser.serializers import TokenCreateSerializer
 from pytest_django.fixtures import SettingsWrapper
 from rest_framework.exceptions import PermissionDenied
 
@@ -145,3 +149,46 @@ def test_invite_link_validation_mixin_validate_fails_if_invite_link_hash_not_val
 
     # Then
     assert exc_info.value.detail == USER_REGISTRATION_WITHOUT_INVITE_ERROR_MESSAGE
+
+
+@pytest.fixture
+def django_ldap_username_field(
+    django_user_model: type[AbstractUser],
+) -> typing.Generator[str, None, None]:
+    ldap_username_field = "username"
+    username_field = django_user_model.USERNAME_FIELD
+    django_user_model.USERNAME_FIELD = ldap_username_field
+    yield ldap_username_field
+    django_user_model.USERNAME_FIELD = username_field
+
+
+# Previously, Djoser's default `TokenCreateSerializer` only respected the
+# Djoser `LOGIN_FIELD` setting so it was impossible to grab the email from
+# serializer and send it as a username to the login backend — which is required for LDAP to work.
+# After Djoser 2.3.0, it's possible to alter `TokenCreateSerializer` behaviour
+# to support this by setting the Django user model's `USERNAME_FIELD` constant
+# to `"username"`, and Djoser's `LOGIN_FIELD` to `"email"`.
+# This test is here to make sure Djoser behaves as expected.
+def test_djoser_token_create_serializer__user_model_username_field__call_expected(
+    mocker: MockerFixture,
+    django_ldap_username_field: str,
+) -> None:
+    # Given
+    expected_username = "some_username"
+    expected_password = "some_password"
+
+    mocked_authenticate = mocker.patch("djoser.serializers.authenticate")
+    serializer = TokenCreateSerializer(
+        data={"email": expected_username, "password": expected_password}
+    )
+    expected_authenticate_kwargs = {
+        "request": None,
+        django_ldap_username_field: expected_username,
+        "password": expected_password,
+    }
+
+    # When
+    serializer.is_valid(raise_exception=True)
+
+    # Then
+    mocked_authenticate.assert_called_with(**expected_authenticate_kwargs)
diff --git a/api/users/models.py b/api/users/models.py
index 2030ad05c3f7..2f0487a4592d 100644
--- a/api/users/models.py
+++ b/api/users/models.py
@@ -113,7 +113,7 @@ class FFAdminUser(LifecycleModel, AbstractUser):
 
     uuid = models.UUIDField(default=uuid.uuid4, editable=False, unique=True)
 
-    USERNAME_FIELD = "email"
+    USERNAME_FIELD = "username" if settings.LDAP_ENABLED else "email"
     REQUIRED_FIELDS = ["first_name", "last_name", "sign_up_type"]
 
     class Meta: