diff --git a/README.md b/README.md
index 128e84f..bade689 100644
--- a/README.md
+++ b/README.md
@@ -136,6 +136,9 @@ The `RedisTaskBackend` accepts the following options under `OPTIONS` in your
 
 A task whose lease expired reaches the `retry` callback as an
 `AcknowledgementTimeout` error, or is marked FAILED when nothing retries it.
+A stored retry callback that is gone from the code base fails the task the same
+way, recording an `ImportError` beside the timeout error. The failure is stored
+as a regular result, so it can be requeued or dropped from the inspector.
 Keep `lease_ttl` above your worst-case runtime: a task that outlives its lease
 can still be running, so a retry may execute concurrently with it. The
 acknowledgement of the lease holder wins: the late result of an expired attempt
diff --git a/tests/backends/test_redis.py b/tests/backends/test_redis.py
index 08a8284..a113c84 100644
--- a/tests/backends/test_redis.py
+++ b/tests/backends/test_redis.py
@@ -272,20 +272,20 @@ def test_reap__removes_running_entry_without_task_data(self):
         finally:
             backend.close()
 
-    def test_reap_running_queue__logs_and_continues_when_retry_callback_is_gone(
-        self, caplog
-    ):
-        """A batch keeps reaping when a task's retry callback is gone from the code base."""
+    def test_reap__fails_tasks_when_retry_callback_is_gone(self, caplog):
+        """A batch fails each task whose stored retry callback is gone from the code base."""
         backend = _make_backend(
             "reap_gone_callback_test", lease_ttl=datetime.timedelta(seconds=1)
         )
         try:
+            task_ids = []
             for _index in range(2):
                 task_result = backend.enqueue(boom_no_retry, args=[])
                 acquired = backend.acquire(
                     timeout=datetime.timedelta(seconds=1), worker="worker-1"
                 )
                 assert acquired is not None
+                task_ids.append(task_result.id)
                 _expire_lease(backend, task_result.id)
                 task_key = backend.TASK_KEY.format(
                     prefix=backend.key_prefix, task_id=task_result.id
@@ -298,6 +298,39 @@ def test_reap_running_queue__logs_and_continues_when_retry_callback_is_gone(
                 RedisBroker(backend)._reap_running_queue("default")
 
             assert caplog.text.count("gone from the code base") == 2
+            running_key = backend._segment_key(TaskResultStatus.RUNNING, "default")
+            assert backend.client.zcard(running_key) == 0
+            assert (
+                backend.client.exists(
+                    backend.TASK_KEY.format(
+                        prefix=backend.key_prefix, task_id=task_ids[0]
+                    )
+                )
+                == 0
+            )
+            failed = {
+                result.id: result
+                for result in backend.peek(
+                    "default", status=TaskResultStatus.FAILED, count=0
+                )
+            }
+            assert set(failed) == set(task_ids)
+            for result in failed.values():
+                assert result.status is TaskResultStatus.FAILED
+                assert result.worker_ids == ["worker-1"]
+                assert result.task.retry is None
+                assert result.errors[-1].exception_class_path == "builtins.ImportError"
+            assert (
+                failed[task_ids[0]].errors[-2].exception_class_path
+                == "threadmill.exceptions.AcknowledgementTimeout"
+            )
+
+            # The stored failure is a regular result, so the inspector can requeue it.
+            backend.requeue(failed[task_ids[0]], timezone.now())
+            deferred_key = backend.DEFERRED_KEY.format(
+                prefix=backend.key_prefix, queue_name="default"
+            )
+            assert backend.client.zscore(deferred_key, task_ids[0]) is not None
         finally:
             backend.close()
 
diff --git a/threadmill/backends/redis.py b/threadmill/backends/redis.py
index f6a0630..442c4db 100644
--- a/threadmill/backends/redis.py
+++ b/threadmill/backends/redis.py
@@ -3,6 +3,7 @@
 import collections.abc
 import dataclasses
 import datetime
+import json
 import logging
 import queue
 import random
@@ -98,11 +99,44 @@ def _reap_running_queue(self, queue_name: str) -> None:
             task_id = member.decode()
             try:
                 self._reap_task(task_id)
-            except ImportError:
-                logger.exception(
+            except ImportError as read_error:
+                task_key = self.backend.TASK_KEY.format(
+                    prefix=self.backend.key_prefix, task_id=task_id
+                )
+                data, lease_worker, lease_started_at, lease_token = (
+                    self.backend.client.hmget(
+                        task_key, "data", *self.backend.LEASE_FIELDS
+                    )
+                )
+                payload = json.loads(data)
+                payload["task"].pop("retry", None)
+                logger.error(
                     "Task %r retry callback is gone from the code base; "
-                    "skipping the reap",
+                    "failing the task: %s",
                     task_id,
+                    read_error,
+                )
+                task_result = self.backend._apply_lease(
+                    self.backend.deserialize_task_result(json.dumps(payload)),
+                    worker=lease_worker.decode() if lease_worker else None,
+                    lease_started_at=_parse_lease_started_at(lease_started_at),
+                    lease_token=(
+                        lease_token.decode() if lease_token is not None else None
+                    ),
+                )
+                self.backend.acknowledge(
+                    dataclasses.replace(
+                        task_result,
+                        status=TaskResultStatus.FAILED,
+                        finished_at=timezone.now(),
+                        errors=[
+                            *task_result.errors,
+                            self.backend.create_task_error(
+                                AcknowledgementTimeout("Task processing lease expired.")
+                            ),
+                            self.backend.create_task_error(read_error),
+                        ],
+                    )
                 )
 
     def _reap_task(self, task_id: str) -> None: