Celery signature.link could raise AttributeError if

The Fix

pip install celery==4.4.0rc5

Based on closed celery/celery issue #5808 · 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.

Jump to Verify Open PR/Commit

@@ -1045,7 +1045,13 @@ def link(self, sig):
 
     def link_error(self, sig):
-        sig = sig.clone().set(immutable=True)
+        try:
+            sig = sig.clone().set(immutable=True)

repro.py

[2019-10-31 15:35:07,882: ERROR/ForkPoolWorker-8] Task cancel[5eaedd7c-9d11-42e6-88fd-952b2526ab2a] raised unexpected: AttributeError("'dict' object has no attribute 'link'")
Traceback (most recent call last):
  File "/home/[...]/python3.7/site-packages/celery/app/trace.py", line 385, in trace_task
    R = retval = fun(*args, **kwargs)
  File "/home/[...]/venv/lib/python3.7/site-packages/celery/app/trace.py", line 650, in __protected_call__
    return self.run(*args, **kwargs)
[...]
  File "/home/[...]/venv/lib/python3.7/site-packages/celery/canvas.py", line 1351, in link
    self.body.link(callback)
  File "/home/[...]/venv/lib/python3.7/site-packages/celery/canvas.py", line 1041, in link
    return self.tasks[0].link(sig)
AttributeError: 'dict' object has no attribute 'link'

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==4.4.0rc5\nWhen NOT to use: Do not apply this fix if the signature is expected to be immutable and built correctly.\n\n

Why This Fix Works in Production

Trigger: [2019-10-31 15:35:07,882: ERROR/ForkPoolWorker-8] Task cancel[5eaedd7c-9d11-42e6-88fd-952b2526ab2a] raised unexpected: AttributeError("'dict' object has no…
Mechanism: Fixes an AttributeError when the signature is built with the from_dict class method.
Why the fix works: Fixes an AttributeError when the signature is built with the from_dict class method. (first fixed release: 4.4.0rc5).

Why This Breaks in Prod

Shows up under Python 3.7 in real deployments (not just unit tests).
Surfaces as: [2019-10-31 15:35:07,882: ERROR/ForkPoolWorker-8] Task cancel[5eaedd7c-9d11-42e6-88fd-952b2526ab2a] raised unexpected: AttributeError("'dict' object has no attribute 'link'")

Proof / Evidence

GitHub issue: #5808
Fix PR: https://github.com/celery/celery/pull/5297
First fixed release: 4.4.0rc5
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.34

Discussion

High-signal excerpts from the issue thread (symptoms, repros, edge-cases).

Jump to Sources Open on GitHub

“so https://github.com/celery/celery/pull/5297 didn't fix it fully? can you provide fix with test?”

@auvipy · 2019-10-31 · source

Failure Signature (Search String)

[2019-10-31 15:35:07,882: ERROR/ForkPoolWorker-8] Task cancel[5eaedd7c-9d11-42e6-88fd-952b2526ab2a] raised unexpected: AttributeError("'dict' object has no attribute 'link'")

Error Message

Stack trace

error.txt

Error Message
-------------
[2019-10-31 15:35:07,882: ERROR/ForkPoolWorker-8] Task cancel[5eaedd7c-9d11-42e6-88fd-952b2526ab2a] raised unexpected: AttributeError("'dict' object has no attribute 'link'")
Traceback (most recent call last):
  File "/home/[...]/python3.7/site-packages/celery/app/trace.py", line 385, in trace_task
    R = retval = fun(*args, **kwargs)
  File "/home/[...]/venv/lib/python3.7/site-packages/celery/app/trace.py", line 650, in __protected_call__
    return self.run(*args, **kwargs)
[...]
  File "/home/[...]/venv/lib/python3.7/site-packages/celery/canvas.py", line 1351, in link
    self.body.link(callback)
  File "/home/[...]/venv/lib/python3.7/site-packages/celery/canvas.py", line 1041, in link
    return self.tasks[0].link(sig)
AttributeError: 'dict' object has no attribute 'link'

Minimal Reproduction

repro.py

[2019-10-31 15:35:07,882: ERROR/ForkPoolWorker-8] Task cancel[5eaedd7c-9d11-42e6-88fd-952b2526ab2a] raised unexpected: AttributeError("'dict' object has no attribute 'link'")
Traceback (most recent call last):
  File "/home/[...]/python3.7/site-packages/celery/app/trace.py", line 385, in trace_task
    R = retval = fun(*args, **kwargs)
  File "/home/[...]/venv/lib/python3.7/site-packages/celery/app/trace.py", line 650, in __protected_call__
    return self.run(*args, **kwargs)
[...]
  File "/home/[...]/venv/lib/python3.7/site-packages/celery/canvas.py", line 1351, in link
    self.body.link(callback)
  File "/home/[...]/venv/lib/python3.7/site-packages/celery/canvas.py", line 1041, in link
    return self.tasks[0].link(sig)
AttributeError: 'dict' object has no attribute 'link'

Environment

Python: 3.7

Fix Options (Details)

Option A — Upgrade to fixed release Safe default (recommended)

pip install celery==4.4.0rc5

When NOT to use: Do not apply this fix if the signature is expected to be immutable and built correctly.

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/5297

First fixed release: 4.4.0rc5

Last verified: 2026-02-09. Validate in your environment.

When NOT to Use This Fix

Do not apply this fix if the signature is expected to be immutable and built correctly.

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
4.4.0rc5	Fixed

Related Issues

No related fixes found.

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Related clusters: Configuration error Data consistency Duplicates

Sources

We don’t republish the full GitHub discussion text. Use the links above for context.

Celery signature.link could raise AttributeError if signature is built with from_dict class method (Fix)