Pydantic Error when validating timezone / ZoneInfo union

The Fix

pip install pydantic==2.9.2

Based on closed pydantic/pydantic issue #10407 · 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

@@ -1650,7 +1650,7 @@ def validate_str_is_valid_iana_tz(value: Any, /) -> ZoneInfo:
             try:
                 return ZoneInfo(value)
-            except (ZoneInfoNotFoundError, ValueError):
+            except (ZoneInfoNotFoundError, ValueError, TypeError):
                 raise PydanticCustomError('zoneinfo_str', 'invalid timezone: {value}', {'value': value})

repro.py

from zoneinfo import ZoneInfo
from datetime import timezone
from pydantic import TypeAdapter, ConfigDict

ta = TypeAdapter(ZoneInfo | timezone, config=ConfigDict(arbitrary_types_allowed=True))
assert ta.validate_python(timezone.utc) is timezone.utc

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==2.9.2\nWhen NOT to use: Do not use this fix if the application relies on specific timezone validation behavior.\n\n

Why This Fix Works in Production

Trigger: *** TypeError: expected str, bytes or os.PathLike object, not timezone
Mechanism: TypeError occurs when validating timezone/ZoneInfo union due to invalid type handling
Why the fix works: Fixes a TypeError when validating timezone/ZoneInfo union in Pydantic. (first fixed release: 2.9.2).

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).
TypeError occurs when validating timezone/ZoneInfo union due to invalid type handling
Surfaces as: *** TypeError: expected str, bytes or os.PathLike object, not timezone

Proof / Evidence

GitHub issue: #10407
Fix PR: https://github.com/pydantic/pydantic/pull/10408
First fixed release: 2.9.2
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.38

Discussion

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

Jump to Sources Open on GitHub

“Thanks for the report! I've opened a PR with a fix, should roll out early next week.”

@sydney-runkle · 2024-09-13 · source

Failure Signature (Search String)

*** TypeError: expected str, bytes or os.PathLike object, not timezone

Error Message

Stack trace

error.txt

Error Message
-------------
*** TypeError: expected str, bytes or os.PathLike object, not timezone
Traceback (most recent call last):
  File "/Users/kkirsche/Library/Caches/pypoetry/virtualenvs/projectname-g3Hahb8t-py3.12/lib/python3.12/site-packages/pydantic/main.py", line 209, in __init__
    validated_self = self.__pydantic_validator__.validate_python(data, self_instance=self)
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/kkirsche/Library/Caches/pypoetry/virtualenvs/projectname-g3Hahb8t-py3.12/lib/python3.12/site-packages/pydantic/_internal/_generate_schema.py", line 1659, in validate_str_is_valid_iana_tz
    return ZoneInfo(value)
           ^^^^^^^^^^^^^^^
  File "/Users/kkirsche/.asdf/installs/python/3.12.6/lib/python3.12/zoneinfo/_tzpath.py", line 73, in find_tzfile
    _validate_tzfile_path(key)
  File "/Users/kkirsche/.asdf/installs/python/3.12.6/lib/python3.12/zoneinfo/_tzpath.py", line 86, in _validate_tzfile_path
    if os.path.isabs(path):
       ^^^^^^^^^^^^^^^^^^^
  File "<frozen posixpath>", line 62, in isabs

Minimal Reproduction

repro.py

from zoneinfo import ZoneInfo
from datetime import timezone
from pydantic import TypeAdapter, ConfigDict

ta = TypeAdapter(ZoneInfo | timezone, config=ConfigDict(arbitrary_types_allowed=True))
assert ta.validate_python(timezone.utc) is timezone.utc

Environment

Python: 3.12
Pydantic: 2

What Broke

Application fails to validate timezone data, causing runtime errors in production.

Why It Broke

TypeError occurs when validating timezone/ZoneInfo union due to invalid type handling

Fix Options (Details)

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

pip install pydantic==2.9.2

When NOT to use: Do not use this fix if the application relies on specific timezone validation behavior.

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/10408

First fixed release: 2.9.2

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

When NOT to Use This Fix

Do not use this fix if the application relies on specific timezone validation behavior.

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
2.9.2	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 Error when validating timezone / ZoneInfo union (Fix)