diff --git a/plinth/modules/upgrades/distupgrade.py b/plinth/modules/upgrades/distupgrade.py
index 964ac66fa..d32aace94 100644
--- a/plinth/modules/upgrades/distupgrade.py
+++ b/plinth/modules/upgrades/distupgrade.py
@@ -116,6 +116,9 @@ def _get_sources_list_codename() -> str | None:
     dists = set()
     for match_ in aug.match('*'):
         dist = aug.get(match_ + '/distribution')
+        if not dist:
+            continue
+
         dist = dist.removesuffix('-updates')
         dist = dist.removesuffix('-security')
         dists.add(dist)
diff --git a/plinth/modules/upgrades/tests/test_distupgrade.py b/plinth/modules/upgrades/tests/test_distupgrade.py
index 6484c9f6f..52f3cfaff 100644
--- a/plinth/modules/upgrades/tests/test_distupgrade.py
+++ b/plinth/modules/upgrades/tests/test_distupgrade.py
@@ -190,7 +190,7 @@ def test_get_status(check_auto, is_dist_upgrade_enabled,
     assert status['current_release_date'] == current_date
     assert status['next_codename'] == 'trixie'
     assert status['next_version'] == 13
-    next_date = datetime_original(2025, 8, 20, tzinfo=timezone.utc)
+    next_date = datetime_original(2025, 8, 9, tzinfo=timezone.utc)
     assert status['next_release_date'] == next_date
     assert status['next_action'] == 'manual'