diff --git a/tests/test_updater_top_level_update.py b/tests/test_updater_top_level_update.py
index 6d1655d1e8..b5d12fef25 100644
--- a/tests/test_updater_top_level_update.py
+++ b/tests/test_updater_top_level_update.py
@@ -18,9 +18,11 @@
 from tests.repository_simulator import RepositorySimulator
 from tuf.api.exceptions import (
     BadVersionNumberError,
+    DownloadError,
     DownloadLengthMismatchError,
     ExpiredMetadataError,
     LengthOrHashMismatchError,
+    RepositoryError,
     UnsignedMetadataError,
 )
 from tuf.api.metadata import (
@@ -755,8 +757,11 @@ def test_refresh_with_offline(self, mock_time: Mock) -> None:
             updater.config.offline = False
             try:
                 updater.refresh()
-            except ExpiredMetadataError:
-                self.assertTrue(True)
+            except Exception as e:
+                self.assertRaises(
+                    (OSError, RepositoryError, DownloadError),
+                    f"unexpected error raised {e}",
+                )
 
         # Make sure local metadata is available
         updater = self._init_updater()
@@ -782,7 +787,7 @@ def test_refresh_with_offline(self, mock_time: Mock) -> None:
         self.sim.update_snapshot()
 
         # Offline flag is set and local metadata is expired. New timestamp
-        # is available but should raise MetaDataError.
+        # is available but should raise ExpiredMetaDataError.
         mock_time.utcnow.return_value = (
             self.sim.safe_expiry - datetime.timedelta(days=6)
         )
@@ -793,7 +798,7 @@ def test_refresh_with_offline(self, mock_time: Mock) -> None:
             try:
                 updater.refresh()
             except ExpiredMetadataError:
-                self.assertFalse(False)
+                self.assertTrue(True)
 
         # Clean up fetch tracker data
         self.sim.fetch_tracker.metadata.clear()
diff --git a/tuf/ngclient/_internal/trusted_metadata_set.py b/tuf/ngclient/_internal/trusted_metadata_set.py
index 1825e33a01..235a3be8c6 100644
--- a/tuf/ngclient/_internal/trusted_metadata_set.py
+++ b/tuf/ngclient/_internal/trusted_metadata_set.py
@@ -251,7 +251,8 @@ def update_timestamp(self, data: bytes) -> Metadata[Timestamp]:
         logger.debug("Updated timestamp v%d", new_timestamp.signed.version)
 
         # timestamp is loaded: raise if it is not valid _final_ timestamp
-        self._check_final_timestamp() if not self.offline else None
+        if not self.offline:
+            self._check_final_timestamp()
 
         return new_timestamp
 
@@ -301,7 +302,8 @@ def update_snapshot(
         logger.debug("Updating snapshot")
 
         # Snapshot cannot be loaded if final timestamp is expired
-        self._check_final_timestamp() if not self.offline else None
+        if not self.offline:
+            self._check_final_timestamp()
 
         snapshot_meta = self.timestamp.signed.snapshot_meta
 
diff --git a/tuf/ngclient/config.py b/tuf/ngclient/config.py
index 11a8fd3c09..98c574df8d 100644
--- a/tuf/ngclient/config.py
+++ b/tuf/ngclient/config.py
@@ -8,6 +8,7 @@
 
 
 @dataclass
+# pylint: disable=too-many-instance-attributes
 class UpdaterConfig:
     """Used to store ``Updater`` configuration.
 
diff --git a/tuf/ngclient/updater.py b/tuf/ngclient/updater.py
index 7c9b1af051..e24d6ed0c0 100644
--- a/tuf/ngclient/updater.py
+++ b/tuf/ngclient/updater.py
@@ -405,7 +405,7 @@ def _load_targets(self, role: str, parent_role: str) -> Metadata[Targets]:
         except (OSError, exceptions.RepositoryError) as e:
             # fails if local data is unavalible and in offline mode
             if self.config.offline:
-                raise exception.DownloadError("Local metadata is missing; cannot download new metadata in offline mode")
+                raise exceptions.DownloadError("Local metadata is missing; cannot download new metadata in offline mode")
             # Local 'role' does not exist or is invalid: update from remote
             logger.debug("Failed to load local %s: %s", role, e)