Requests cannot use json() on request in python 3.7

The Fix

pip install requests==2.27.0

Based on closed psf/requests issue #4879 · 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

@@ -115,3 +115,4 @@ Patches and Suggestions
 - André Graf (dergraf)
 - Stephen Zhuang (everbird)
+- Martijn Pieters
diff --git a/requests/models.py b/requests/models.py
index c19d3ccab7..06c8a71a3e 100644

repro.py

import requests
jsonstr="{ 'bla' : 'blub'}"
resp = requests.Response()
resp._content = jsonstr
resp.json()

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3/dist-packages/requests/models.py", line 880, in json
    encoding = guess_json_utf(self.content)
  File "/usr/lib/python3/dist-packages/requests/utils.py", line 798, in guess_json_utf
    nullcount = sample.count(_null)
TypeError: must be str, not bytes

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 requests==2.27.0\nWhen NOT to use: This fix is not applicable if the content is not properly set to bytes.\n\n

Why This Fix Works in Production

Trigger: import requests
Mechanism: The _null constant was incorrectly encoded to bytes, causing a TypeError in Python 3
Why the fix works: Introduces a JSON-specific encoding detection for responses without specified encoding, addressing issues related to type errors in Python 3. (first fixed release: 2.27.0).

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 3.7 in real deployments (not just unit tests).
The _null constant was incorrectly encoded to bytes, causing a TypeError in Python 3
Surfaces as: import requests

Proof / Evidence

GitHub issue: #4879
Fix PR: https://github.com/psf/requests/pull/909
First fixed release: 2.27.0
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.50

Discussion

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

Jump to Sources Open on GitHub

“for anyone else who get this error - just make content bytes”

@Smosker · 2019-11-06 · source

“So it is possible in python. Just nobody bothered. This is what I found in base64: warnings.warn("encodestring() is a deprecated alias since 3.1, " "use…”

@uvwild · 2018-11-26 · source

“Forgive me if I'm misunderstanding but setting Response._content to a value seems like mucking with internals which has no guarantees compared to the "public" interface”

@sethmlarson · 2018-11-26 · source

“@SethMichaelLarson is correct, this is outside of Requests defined usage”

@nateprewitt · 2018-11-26 · source

Failure Signature (Search String)

import requests

Error Message

Stack trace

error.txt

Error Message
-------------
import requests
jsonstr="{ 'bla' : 'blub'}"
resp = requests.Response()
resp._content = jsonstr
resp.json()

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3/dist-packages/requests/models.py", line 880, in json
    encoding = guess_json_utf(self.content)
  File "/usr/lib/python3/dist-packages/requests/utils.py", line 798, in guess_json_utf
    nullcount = sample.count(_null)
TypeError: must be str, not bytes

Minimal Reproduction

repro.py

import requests
jsonstr="{ 'bla' : 'blub'}"
resp = requests.Response()
resp._content = jsonstr
resp.json()

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3/dist-packages/requests/models.py", line 880, in json
    encoding = guess_json_utf(self.content)
  File "/usr/lib/python3/dist-packages/requests/utils.py", line 798, in guess_json_utf
    nullcount = sample.count(_null)
TypeError: must be str, not bytes

Environment

Python: 3.7

What Broke

TypeError occurs when calling json() on a response with improperly set content.

Why It Broke

The _null constant was incorrectly encoded to bytes, causing a TypeError in Python 3

Fix Options (Details)

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

pip install requests==2.27.0

When NOT to use: This fix is not applicable if the content is not properly set to bytes.

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

Fix reference: https://github.com/psf/requests/pull/909

First fixed release: 2.27.0

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

When NOT to Use This Fix

This fix is not applicable if the content is not properly set to bytes.

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 TLS smoke test that performs a real handshake in CI (include CA bundle validation and hostname checks).
Alert on handshake failures by error string and endpoint to catch cert/CA changes quickly.

Version Compatibility Table

Version	Status
2.27.0	Fixed

Related Issues

No related fixes found.

Cluster: requests:configuration-error Requests hub Requests best practices All hubs All clusters

Related clusters: Data consistency SSL handshake Other

Sources

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

Requests cannot use json() on request in python 3.7 (TypeError: must be str, not bytes) (Fix)