httpx Content-Length header is missing in

The Fix

Upgrade to version 0.13.2 or later.

Based on closed encode/httpx issue #987 · 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

@@ -616,6 +616,9 @@ def prepare(self) -> None:
 
         has_host = "host" in self.headers
+        has_content_length = (
+            "content-length" in self.headers or "transfer-encoding" in self.headers
+        )

repro.py

import requests
import httpx

for client in (requests, httpx):
    for method in ("get", "head", "delete", "post", "put", "patch"):
        r = client.request(method, f"https://httpbin.org/headers")
        print(
            f"[{client.__name__}] method={method.upper()} "
            f'Content-Length={r.request.headers.get("Content-Length")}'
        )

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\nUpgrade to version 0.13.2 or later.\nWhen NOT to use: Do not apply this fix if the server does not require Content-Length for empty payloads.\n\n

Why This Fix Works in Production

Trigger: Content-Length header is missing in POST/DELETE/PUT/PATCH requests without body
Mechanism: Content-Length header is not added for POST, PUT, and PATCH requests without a body
Why the fix works: Add 'Content-Length: 0' on POST, PUT, PATCH if required. (first fixed release: 0.13.2).

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

Content-Length header is not added for POST, PUT, and PATCH requests without a body
Production symptom (often without a traceback): Content-Length header is missing in POST/DELETE/PUT/PATCH requests without body

Proof / Evidence

GitHub issue: #987
Fix PR: https://github.com/encode/httpx/pull/995
First fixed release: 0.13.2
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.53

Discussion

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

Jump to Sources Open on GitHub

“I believe this is a bug as we're not following the RFC: > A user agent SHOULD send a Content-Length in a request message when…”

@yeraydiazdiaz · 2020-05-24 · source

“I’d suggest auto including it in Request.prepare, if the method requires one, and none is currently present.”

@lovelydinosaur · 2020-05-24 · source

“^Sounds good to me too — let the content stream not return a Content-Length if there's no body, and add a default Content-Length: 0 in…”

@florimondmanca · 2020-05-24 · source

“We should cover POST, PUT, and PATCH here”

@lovelydinosaur · 2020-05-25 · source

Failure Signature (Search String)

Content-Length header is missing in POST/DELETE/PUT/PATCH requests without body
I am not sure how to classify this issue: it could be a bug, since it is an incompatible with `requests`, on the other hand, it could be feature request, if you consider it is not

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Content-Length header is missing in POST/DELETE/PUT/PATCH requests without body
I am not sure how to classify this issue: it could be a bug, since it is an incompatible with `requests`, on the other hand, it could be feature request, if you consider it is not that important. So, I decided to go with question. :D

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Content-Length header is missing in POST/DELETE/PUT/PATCH requests without body
I am not sure how to classify this issue: it could be a bug, since it is an incompatible with `requests`, on the other hand, it could be feature request, if you consider it is not that important. So, I decided to go with question. :D

Minimal Reproduction

repro.py

import requests
import httpx

for client in (requests, httpx):
    for method in ("get", "head", "delete", "post", "put", "patch"):
        r = client.request(method, f"https://httpbin.org/headers")
        print(
            f"[{client.__name__}] method={method.upper()} "
            f'Content-Length={r.request.headers.get("Content-Length")}'
        )

What Broke

Requests to the server fail with a 411 Client Error when no Content-Length is present.

Why It Broke

Content-Length header is not added for POST, PUT, and PATCH requests without a body

Fix Options (Details)

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

Upgrade to version 0.13.2 or later.

When NOT to use: Do not apply this fix if the server does not require Content-Length for empty payloads.

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

Fix reference: https://github.com/encode/httpx/pull/995

First fixed release: 0.13.2

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

When NOT to Use This Fix

Do not apply this fix if the server does not require Content-Length for empty payloads.

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
0.13.2	Fixed

Related Issues

No related fixes found.

Cluster: httpx:configuration-error All hubs All clusters

Related clusters: Data consistency Other Timeout

Sources

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

httpx Content-Length header is missing in POST/DELETE/PUT/PATCH requests without body (Fix)