diff --git a/changelog.d/14821.misc b/changelog.d/14821.misc
new file mode 100644
index 0000000000..99e4e5e8a1
--- /dev/null
+++ b/changelog.d/14821.misc
@@ -0,0 +1 @@
+Re-enable some linting that was disabled when we switched to ruff.
diff --git a/pyproject.toml b/pyproject.toml
index 740d33066e..10d50ddb45 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -48,11 +48,6 @@ line-length = 88
 #  E731: do not assign a lambda expression, use a def
 #  E501: Line too long (black enforces this for us)
 #
-# See https://github.com/charliermarsh/ruff/#pyflakes
-#  F401: unused import
-#  F811: Redefinition of unused
-#  F821: Undefined name
-#
 # flake8-bugbear compatible checks. Its error codes are described at
 # https://github.com/charliermarsh/ruff/#flake8-bugbear
 #  B019: Use of functools.lru_cache or functools.cache on methods can lead to memory leaks
@@ -64,9 +59,6 @@ ignore = [
     "B024",
     "E501",
     "E731",
-    "F401",
-    "F811",
-    "F821",
 ]
 select = [
     # pycodestyle checks.
diff --git a/stubs/sortedcontainers/sortedlist.pyi b/stubs/sortedcontainers/sortedlist.pyi
index cd4c969849..1fe1a136f1 100644
--- a/stubs/sortedcontainers/sortedlist.pyi
+++ b/stubs/sortedcontainers/sortedlist.pyi
@@ -7,7 +7,6 @@ from __future__ import annotations
 from typing import (
     Any,
     Callable,
-    Generic,
     Iterable,
     Iterator,
     List,
diff --git a/stubs/sortedcontainers/sortedset.pyi b/stubs/sortedcontainers/sortedset.pyi
index d761c438f7..6db11eacbe 100644
--- a/stubs/sortedcontainers/sortedset.pyi
+++ b/stubs/sortedcontainers/sortedset.pyi
@@ -5,10 +5,8 @@
 from __future__ import annotations
 
 from typing import (
-    AbstractSet,
     Any,
     Callable,
-    Generic,
     Hashable,
     Iterable,
     Iterator,
diff --git a/stubs/synapse/synapse_rust/push.pyi b/stubs/synapse/synapse_rust/push.pyi
index b91f2edd7b..373b40740b 100644
--- a/stubs/synapse/synapse_rust/push.pyi
+++ b/stubs/synapse/synapse_rust/push.pyi
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Any, Collection, Dict, Mapping, Optional, Sequence, Set, Tuple, Union
+from typing import Any, Collection, Dict, Mapping, Optional, Sequence, Tuple, Union
 
 from synapse.types import JsonDict
 
diff --git a/synapse/config/_base.pyi b/synapse/config/_base.pyi
index bd265de536..b5cec132b4 100644
--- a/synapse/config/_base.pyi
+++ b/synapse/config/_base.pyi
@@ -1,5 +1,3 @@
-from __future__ import annotations
-
 import argparse
 from typing import (
     Any,
@@ -20,7 +18,7 @@ from typing import (
 
 import jinja2
 
-from synapse.config import (
+from synapse.config import (  # noqa: F401
     account_validity,
     api,
     appservice,
@@ -169,7 +167,7 @@ class RootConfig:
         self, section_name: Literal["caches"]
     ) -> cache.CacheConfig: ...
     @overload
-    def reload_config_section(self, section_name: str) -> Config: ...
+    def reload_config_section(self, section_name: str) -> "Config": ...
 
 class Config:
     root: RootConfig
@@ -202,9 +200,9 @@ def find_config_files(search_paths: List[str]) -> List[str]: ...
 class ShardedWorkerHandlingConfig:
     instances: List[str]
     def __init__(self, instances: List[str]) -> None: ...
-    def should_handle(self, instance_name: str, key: str) -> bool: ...
+    def should_handle(self, instance_name: str, key: str) -> bool: ...  # noqa: F811
 
 class RoutableShardedWorkerHandlingConfig(ShardedWorkerHandlingConfig):
-    def get_instance(self, key: str) -> str: ...
+    def get_instance(self, key: str) -> str: ...  # noqa: F811
 
 def read_file(file_path: Any, config_path: Iterable[str]) -> str: ...
diff --git a/tests/storage/test_event_push_actions.py b/tests/storage/test_event_push_actions.py
index 5fa8bd2d98..76c06a9d1e 100644
--- a/tests/storage/test_event_push_actions.py
+++ b/tests/storage/test_event_push_actions.py
@@ -154,7 +154,7 @@ class EventPushActionsStoreTestCase(HomeserverTestCase):
         # Create a user to receive notifications and send receipts.
         user_id, token, _, other_token, room_id = self._create_users_and_room()
 
-        last_event_id: str
+        last_event_id = ""
 
         def _assert_counts(notif_count: int, highlight_count: int) -> None:
             counts = self.get_success(
@@ -289,7 +289,7 @@ class EventPushActionsStoreTestCase(HomeserverTestCase):
         user_id, token, _, other_token, room_id = self._create_users_and_room()
         thread_id: str
 
-        last_event_id: str
+        last_event_id = ""
 
         def _assert_counts(
             notif_count: int,
@@ -471,7 +471,7 @@ class EventPushActionsStoreTestCase(HomeserverTestCase):
         user_id, token, _, other_token, room_id = self._create_users_and_room()
         thread_id: str
 
-        last_event_id: str
+        last_event_id = ""
 
         def _assert_counts(
             notif_count: int,