diff --git a/changelog.d/20068.misc b/changelog.d/20068.misc
new file mode 100644
index 0000000000..cb2766e80a
--- /dev/null
+++ b/changelog.d/20068.misc
@@ -0,0 +1 @@
+Routinely purge old cancelled tasks from the database.
diff --git a/synapse/util/task_scheduler.py b/synapse/util/task_scheduler.py
index c1790fd3ae..c01ddf7339 100644
--- a/synapse/util/task_scheduler.py
+++ b/synapse/util/task_scheduler.py
@@ -400,10 +400,10 @@ class TaskScheduler:
         """Clean old complete or failed jobs to avoid clutter the DB."""
         now = self._clock.time_msec()
         for task in await self._store.get_scheduled_tasks(
-            statuses=[TaskStatus.FAILED, TaskStatus.COMPLETE],
+            statuses=[TaskStatus.FAILED, TaskStatus.CANCELLED, TaskStatus.COMPLETE],
             max_timestamp=now - TaskScheduler.KEEP_TASKS_FOR_MS,
         ):
-            # FAILED and COMPLETE tasks should never be running
+            # FAILED, CANCELLED and COMPLETE tasks should never be running
             assert task.id not in self._running_tasks
             await self._store.delete_scheduled_task(task.id)