The Fix
pip install celery==5.6.0
Based on closed celery/celery issue #9006 · PR/commit linked
Production note: This usually shows up under retries/timeouts. Treat it as a side-effect risk until you can verify behavior with a canary + real traffic.
@@ -540,7 +540,7 @@ def on_chord_part_return(self, request, state, result,
total = int(chord_size_bytes) + totaldiff
if readycount == total:
- header_result = GroupResult.restore(gid)
+ header_result = GroupResult.restore(gid, app=app)
if header_result is not None:
repro.py
software -> celery:5.2.7 (dawn-chorus) kombu:5.3.7 py:3.8.0
billiard:3.6.4.0 py-amqp:5.2.0
platform -> system:Linux arch:64bit, ELF
kernel version:5.10.213-201.855.amzn2.x86_64 imp:CPython
loader -> celery.loaders.default.Loader
settings -> transport:amqp results:disabled
deprecated_settings: None
verify
Re-run the minimal reproduction on your broken version, then apply the fix and re-run.
fix.md
Option A — Upgrade to fixed release\npip install celery==5.6.0\nWhen NOT to use: This fix should not be applied if using a different backend or app configuration.\n\n
Why This Fix Works in Production
- Trigger: raised: AttributeError("'DisabledBackend' object has no attribute '_restore_group'")
- Mechanism: The error occurs due to the incorrect Celery app being used, which lacks a defined result backend
- Why the fix works: Fixes an AttributeError encountered when executing nested chords with a Redis backend by ensuring the correct Celery app is passed to the GroupResult.restore method. (first fixed release: 5.6.0).
Production impact:
- If left unfixed, the same config can fail only in production (env differences), causing startup failures or partial feature outages.
Why This Breaks in Prod
- Shows up under Python 3.8 in real deployments (not just unit tests).
- The error occurs due to the incorrect Celery app being used, which lacks a defined result backend
- Surfaces as: raised: AttributeError("'DisabledBackend' object has no attribute '_restore_group'")
Proof / Evidence
- GitHub issue: #9006
- Fix PR: https://github.com/celery/celery/pull/9950
- First fixed release: 5.6.0
- Reproduced locally: No (not executed)
- Last verified: 2026-02-09
- Confidence: 0.85
- Did this fix it?: Yes (upstream fix exists)
- Own content ratio: 0.47
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“@mahendrap1512 well the DisabledBackend error suggests that Celery doesn't have a result backend configured properly”
“Hi, I got the same problem on celery 5.4.0, redis as a result backend and this type of usage : chord([task1, task2], callback) result backend…”
“Hey @manens check if you are doing worker sharing or not (if the same worker is listening to multiple queues). We were facing this when…”
“I have opened a pull request for the same bug. https://github.com/celery/celery/pull/9950”
Failure Signature (Search String)
- raised: AttributeError("'DisabledBackend' object has no attribute '_restore_group'")
Error Message
Stack trace
error.txt
Error Message
-------------
raised: AttributeError("'DisabledBackend' object has no attribute '_restore_group'")
Traceback (most recent call last):
File "/usr/local/lib/python3.8/dist-packages/celery/backends/redis.py", line 488, in on_chord_part_return
header_result = GroupResult.restore(gid)
File "/usr/local/lib/python3.8/dist-packages/celery/result.py", line 960, in restore
return backend.restore_group(id)
File "/usr/local/lib/python3.8/dist-packages/celery/backends/base.py", line 656, in restore_group
meta = self.get_group_meta(group_id, cache=cache)
File "/usr/local/lib/python3.8/dist-packages/celery/backends/base.py", line 649, in get_group_meta
meta = self._restore_group(group_id)
AttributeError: 'DisabledBackend' object has no attribute '_restore_group'
Minimal Reproduction
repro.py
software -> celery:5.2.7 (dawn-chorus) kombu:5.3.7 py:3.8.0
billiard:3.6.4.0 py-amqp:5.2.0
platform -> system:Linux arch:64bit, ELF
kernel version:5.10.213-201.855.amzn2.x86_64 imp:CPython
loader -> celery.loaders.default.Loader
settings -> transport:amqp results:disabled
deprecated_settings: None
Environment
- Python: 3.8
What Broke
Intermittent failures when executing nested chords lead to AttributeError in production.
Why It Broke
The error occurs due to the incorrect Celery app being used, which lacks a defined result backend
Fix Options (Details)
Option A — Upgrade to fixed release Safe default (recommended)
pip install celery==5.6.0
When NOT to use: This fix should not be applied if using a different backend or app configuration.
Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.
Fix reference: https://github.com/celery/celery/pull/9950
First fixed release: 5.6.0
Last verified: 2026-02-09. Validate in your environment.
When NOT to Use This Fix
- This fix should not be applied if using a different backend or app configuration.
Verify Fix
verify
Re-run the minimal reproduction on your broken version, then apply the fix and re-run.
Did This Fix Work in Your Case?
Quick signal helps us prioritize which fixes to verify and improve.
Prevention
- Capture the exact failing error string in logs and tests so you can reproduce via a minimal script.
- Pin production dependencies and upgrade only with a reproducible test that hits the failing path.
Version Compatibility Table
| Version | Status |
|---|---|
| 5.6.0 | Fixed |
Related Issues
No related fixes found.
Sources
We don’t republish the full GitHub discussion text. Use the links above for context.