Pydantic False positive 'Invalid value for "Config.extra"

The Fix

pip install pydantic==1.10.15

Based on closed pydantic/pydantic issue #9021 · PR/commit linked

Production note: Most teams hit this during upgrades or environment changes. Roll out with a canary and smoke critical endpoints (health, OpenAPI/docs) before 100%.

Jump to Verify Open PR/Commit

@@ -550,7 +550,7 @@ def collect_config(self) -> ModelConfigData:  # noqa: C901 (ignore complexity)
                         if arg_name is None:
                             continue
-                        config.update(self.get_config_update(arg_name, arg))
+                        config.update(self.get_config_update(arg_name, arg, lax_extra=True))
                 elif isinstance(stmt.rvalue, DictExpr):  # dict literals

repro.py

# test.py
from pydantic import BaseModel, ConfigDict

def condition() -> bool:
    return True

class MyModel(BaseModel):
    model_config = ConfigDict(extra="ignore" if condition() else "forbid")

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 pydantic==1.10.15\nWhen NOT to use: Do not use if it changes public behavior or if the failure cannot be reproduced.\n\n

Why This Fix Works in Production

Trigger: test.py:10: error: Invalid value for "Config.extra" [pydantic-config]
Mechanism: Removes an unnecessary warning for the config in the Pydantic mypy plugin, addressing a false positive error related to the 'Config.extra' value.
Why the fix works: Removes an unnecessary warning for the config in the Pydantic mypy plugin, addressing a false positive error related to the 'Config.extra' value. (first fixed release: 1.10.15).

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 3.12 in real deployments (not just unit tests).
Production symptom (often without a traceback): test.py:10: error: Invalid value for "Config.extra" [pydantic-config]

Proof / Evidence

GitHub issue: #9021
Fix PR: https://github.com/pydantic/pydantic/pull/9039
First fixed release: 1.10.15
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.57

Discussion

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

Jump to Sources Open on GitHub

“@Viicos is right; suggested approach compatible with mypy: I haven't confirmed this works but I think it should”

@dmontagu · 2024-03-15 · source

“@Apakottur, Hmm, thanks for reporting this. Seems like a bug, but a pretty minor one. Maybe @dmontagu has an idea for an easy fix...”

@sydney-runkle · 2024-03-15 · source

“This has to do with how mypy handles union of types (see playground). I don't think Pydantic can do much here. For reference, pyright will…”

@Viicos · 2024-03-15 · source

“Thanks for the respone @dmontagu , I've tried both your suggestions and they both still give the same error. Does one of them pass without…”

@Apakottur · 2024-03-18 · source

Failure Signature (Search String)

test.py:10: error: Invalid value for "Config.extra" [pydantic-config]
Found 1 error in 1 file (checked 1 source file)

Copy-friendly signature

signature.txt

Failure Signature
-----------------
test.py:10: error: Invalid value for "Config.extra"  [pydantic-config]
Found 1 error in 1 file (checked 1 source file)

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
test.py:10: error: Invalid value for "Config.extra"  [pydantic-config]
Found 1 error in 1 file (checked 1 source file)

Minimal Reproduction

repro.py

# test.py
from pydantic import BaseModel, ConfigDict

def condition() -> bool:
    return True

class MyModel(BaseModel):
    model_config = ConfigDict(extra="ignore" if condition() else "forbid")

Environment

Python: 3.12
Pydantic: 2

Fix Options (Details)

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

pip install pydantic==1.10.15

When NOT to use: Do not use if it changes public behavior or if the failure cannot be reproduced.

Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.

Fix reference: https://github.com/pydantic/pydantic/pull/9039

First fixed release: 1.10.15

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

When NOT to Use This Fix

Do not use if it changes public behavior or if the failure cannot be reproduced.

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

Add a CI check that diffs key outputs after upgrades (OpenAPI schema snapshots, JSON payload shapes, CLI output).
Upgrade behind a canary and run integration tests against the canary before 100% rollout.

Version Compatibility Table

Version	Status
1.10.15	Fixed

Related Issues

No related fixes found.

Cluster: pydantic:configuration-error Pydantic hub Pydantic best practices All hubs All clusters

Related clusters: Data consistency OpenAPI schema Serialization

Sources

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

Pydantic False positive 'Invalid value for "Config.extra" [pydantic-config]' (Fix)