Pydantic Unexpected error message while using properties

The Fix

pip install pydantic==1.10.15

Based on closed pydantic/pydantic issue #9070 · 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

@@ -764,7 +764,7 @@ def __getattr__(self, item: str) -> Any:
                     pydantic_extra = None
 
-                if pydantic_extra is not None:
+                if pydantic_extra:
                     try:

repro.py

from pydantic import BaseModel, ConfigDict


class MyModel(BaseModel):

    @property
    def my_property(self):
        """A random property."""
        raise AttributeError("Original Error!")

    model_config = ConfigDict(extra="allow")


my_model = MyModel()
my_model.my_property

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: This fix should not be used if the model requires strict attribute handling without allowing extra fields.\n\n

Why This Fix Works in Production

Trigger: Unexpected error message while using properties with pydantic models
Mechanism: Fixes an issue in Model.__getattr__() that incorrectly handles extra fields when they are empty, leading to misleading AttributeError messages.
Why the fix works: Fixes an issue in Model.__getattr__() that incorrectly handles extra fields when they are empty, leading to misleading AttributeError messages. (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 3.9 in real deployments (not just unit tests).
Production symptom (often without a traceback): Unexpected error message while using properties with pydantic models

Proof / Evidence

GitHub issue: #9070
Fix PR: https://github.com/pydantic/pydantic/pull/9082
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: 0.63

Discussion

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

Jump to Sources Open on GitHub

“@bcdurak, Huh, that's odd! Thanks for reporting. Definitely a bug. Happens when you have the computed_field decorator over said property as well, which is even…”

@sydney-runkle · 2024-03-22 · source

“@sydney-runkle I looked into this and it seems that the problem is in the Model.__getattr__() method”

@NeevCohen · 2024-03-22 · source

Failure Signature (Search String)

Unexpected error message while using properties with pydantic models
I ran into an issue while using a property with a pydantic class which led to an unexpected error.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Unexpected error message while using properties with pydantic models
I ran into an issue while using a property with a pydantic class which led to an unexpected error.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Unexpected error message while using properties with pydantic models
I ran into an issue while using a property with a pydantic class which led to an unexpected error.

Minimal Reproduction

repro.py

from pydantic import BaseModel, ConfigDict


class MyModel(BaseModel):

    @property
    def my_property(self):
        """A random property."""
        raise AttributeError("Original Error!")

    model_config = ConfigDict(extra="allow")


my_model = MyModel()
my_model.my_property

Environment

Python: 3.9
Pydantic: 2

What Broke

Users receive misleading AttributeError messages when accessing properties in Pydantic models.

Fix Options (Details)

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

pip install pydantic==1.10.15

When NOT to use: This fix should not be used if the model requires strict attribute handling without allowing extra fields.

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/9082

First fixed release: 1.10.15

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

When NOT to Use This Fix

This fix should not be used if the model requires strict attribute handling without allowing extra fields.

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 Unexpected error message while using properties with pydantic models (Fix)