diff --git a/social_core/actions.py b/social_core/actions.py
index 2d74149a7..4ac2b43ab 100644
--- a/social_core/actions.py
+++ b/social_core/actions.py
@@ -46,7 +46,7 @@ def do_complete(backend, login, user=None, redirect_name="next", *args, **kwargs
         # clean partial data after usage
         backend.strategy.clean_partial_pipeline(partial.token)
     else:
-        user = backend.complete(user=user, *args, **kwargs)
+        user = backend.complete(user=user, redirect_name=redirect_name, *args, **kwargs)
 
     # pop redirect value before the session is trashed on login(), but after
     # the pipeline so that the pipeline can change the redirect if needed
diff --git a/social_core/tests/actions/actions.py b/social_core/tests/actions/actions.py
index 017b4adc3..9db7a2fff 100644
--- a/social_core/tests/actions/actions.py
+++ b/social_core/tests/actions/actions.py
@@ -53,6 +53,7 @@ class BaseActionTest(unittest.TestCase):
 
     def __init__(self, *args, **kwargs):
         self.strategy = None
+        self.backend = None
         super().__init__(*args, **kwargs)
 
     def setUp(self):
@@ -63,7 +64,9 @@ def setUp(self):
         TestAssociation.reset_cache()
         Backend = module_member("social_core.backends.github.GithubOAuth2")
         self.strategy = self.strategy or TestStrategy(TestStorage)
-        self.backend = Backend(self.strategy, redirect_uri="/complete/github")
+        self.backend = self.backend or Backend(
+            self.strategy, redirect_uri="/complete/github"
+        )
         self.user = None
 
     def tearDown(self):
diff --git a/social_core/tests/actions/test_login.py b/social_core/tests/actions/test_login.py
index 7a5654907..09819fdfe 100644
--- a/social_core/tests/actions/test_login.py
+++ b/social_core/tests/actions/test_login.py
@@ -1,8 +1,33 @@
+from ...backends.base import BaseAuth
 from ...utils import PARTIAL_TOKEN_SESSION_NAME
-from ..models import User
+from ..models import TestUserSocialAuth, User
 from .actions import BaseActionTest
 
 
+class BackendThatControlsRedirect(BaseAuth):
+    """
+    A fake backend that sets the URL to redirect to after login.
+
+    It is not always possible to set the redirect URL in the session state prior to auth and then retrieve it when
+    auth is complete, because the session cookie might not be available post-auth. For example, for SAML, a POST request
+    redirects the user from the IdP (Identity Provider) back to the SP (Service Provider) to complete the auth process,
+    but the session cookie will not be present if the session cookie's `SameSite` attribute is not set to "None".
+    To mitigate this, SAML provides a `RelayState` parameter to pass data like a redirect URL from the SP to the IdP
+    and back again. In that case, the redirect URL is only known in `auth_complete`, and must be communicated back to
+    the `do_complete` action via session state so that it can issue the intended redirect.
+    """
+
+    ACCESS_TOKEN_URL = "https://example.com/oauth/access_token"
+
+    def auth_url(self):
+        return "https://example.com/oauth/auth?state=foo"
+
+    def auth_complete(self, *args, **kwargs):
+        # Put the redirect URL in the session state, as this is where the `do_complete` action looks for it.
+        self.strategy.session_set(kwargs["redirect_name"], "/after-login")
+        return kwargs["user"]
+
+
 class LoginActionTest(BaseActionTest):
     def test_login(self):
         self.do_login()
@@ -37,6 +62,12 @@ def test_redirect_value(self):
         redirect = self.do_login(after_complete_checks=False)
         self.assertEqual(redirect.url, "/after-login")
 
+    def test_redirect_value_set_by_backend(self):
+        self.backend = BackendThatControlsRedirect(self.strategy)
+        self.user = TestUserSocialAuth.create_user("test-user")
+        redirect = self.do_login(after_complete_checks=False)
+        self.assertEqual(redirect.url, "/after-login")
+
     def test_login_with_invalid_partial_pipeline(self):
         def before_complete():
             partial_token = self.strategy.session_get(PARTIAL_TOKEN_SESSION_NAME)