Pydantic Mypy error on __validators_

The Fix

pip install pydantic==1.10.17

Based on closed pydantic/pydantic issue #9690 · 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

@@ -1435,7 +1435,7 @@ def create_model(
     __base__: None = None,
     __module__: str = __name__,
-    __validators__: dict[str, classmethod[Any, ..., Any]] | None = None,
+    __validators__: dict[str, Callable[..., Any]] | None = None,
     __cls_kwargs__: dict[str, Any] | None = None,

repro.py

python -c "import pydantic.version; print(pydantic.version.version_info())"

             pydantic version: 2.7.4
        pydantic-core version: 2.18.4
          pydantic-core build: profile=release pgo=true
                 install path: /Users/foobar/1_10/.venv/lib/python3.11/site-packages/pydantic
               python version: 3.11.4 (main, May 21 2024, 16:01:49) [Clang 15.0.0 (clang-1500.3.9.4)]
                     platform: macOS-14.4.1-arm64-arm-64bit
             related packages: mypy-1.10.0 fastapi-0.105.0 typing_extensions-4.12.2
                       commit: unknown

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==1.10.17\nWhen NOT to use: This fix should not be applied if strict type checking is required.\n\n

Why This Fix Works in Production

Trigger: Mypy error on __validators__ when using create_model
Mechanism: The type specification for __validators__ in create_model was too restrictive
Why the fix works: Relaxed the type specification for `__validators__` values in `create_model` to allow more flexible validator types. (first fixed release: 1.10.17).

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 3.11 in real deployments (not just unit tests).
The type specification for __validators__ in create_model was too restrictive
Production symptom (often without a traceback): Mypy error on __validators__ when using create_model

Proof / Evidence

GitHub issue: #9690
Fix PR: https://github.com/pydantic/pydantic/pull/9697
First fixed release: 1.10.17
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.52

Discussion

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

Jump to Sources Open on GitHub

“@jonathan-hill-visasq, Thanks for reporting this. Agreed, I think we can relax that annotation.”

@sydney-runkle · 2024-06-19 · source

Failure Signature (Search String)

Mypy error on __validators__ when using create_model

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Mypy error on __validators__ when using create_model
from pydantic import ValidationError, create_model, field_validator

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Mypy error on __validators__ when using create_model
from pydantic import ValidationError, create_model, field_validator

Minimal Reproduction

repro.py

python -c "import pydantic.version; print(pydantic.version.version_info())"

             pydantic version: 2.7.4
        pydantic-core version: 2.18.4
          pydantic-core build: profile=release pgo=true
                 install path: /Users/foobar/1_10/.venv/lib/python3.11/site-packages/pydantic
               python version: 3.11.4 (main, May 21 2024, 16:01:49) [Clang 15.0.0 (clang-1500.3.9.4)]
                     platform: macOS-14.4.1-arm64-arm-64bit
             related packages: mypy-1.10.0 fastapi-0.105.0 typing_extensions-4.12.2
                       commit: unknown

Environment

Python: 3.11
Pydantic: 2

What Broke

Mypy raises type errors when using create_model with custom validators.

Why It Broke

The type specification for __validators__ in create_model was too restrictive

Fix Options (Details)

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

pip install pydantic==1.10.17

When NOT to use: This fix should not be applied if strict type checking is required.

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/9697

First fixed release: 1.10.17

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

When NOT to Use This Fix

This fix should not be applied if strict type checking is required.

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
1.10.17	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 Mypy error on __validators__ when using create_model (Fix)