Issue with formData post request with latest 6.24.1 version #4918
Description
Bug Description
Hi everyone,
I encountered an issue with multipart/form-data fetch requests after upgrading from 6.24.0 to 6.24.1.
Could you please investigate.
Reproducible By
From a quick look while debugging, I’m passing the same data to undici’s fetch in both versions. =>
fetchParams {
method: 'POST',
headers: {
accept: 'application/json, application/problem+json',
authorization: 'Bearer ......'
},
body: FormData {
name: 'some',
someOtherProperty: '8000'
},
redirect: 'follow',
signal: AbortSignal { aborted: false }
}
But starting from 6.24.1 I noticed that my generic NestAPI receives undefined values for the same endpoint.
✗ POST /some-endpoint
Request URL: http://localhost:4096/some
Request Headers:
accept: application/json, application/problem+json
authorization: Bearer ********
Request Body:
{
"name": "some",
"someOtherProperty": "8000",
}
Response status code: 400
Response time: 2 ms
Response Headers:
access-control-allow-credentials: true
connection: keep-alive
content-length: 445
content-type: application/problem+json; charset=utf-8
date: Fri, 20 Mar 2026 12:58:31 GMT
etag: W/"1bd-V4YJteIrvGmGoHeCtvLwBMlEjS0"
keep-alive: timeout=5
vary: Origin
x-powered-by: Express
Response Size: 445 bytes
Response Body:
{
"type": "about:blank",
"title": "Validation failed",
"code": "BAD_REQUEST",
"message": "Validation failed",
"errors": [
{
"code": "invalid_type",
"expected": "string",
"received": "undefined",
"path": [
"name"
],
"message": "Required"
},
{
"code": "invalid_type",
"expected": "string",
"received": "undefined",
"path": [
"someOtherProperty"
],
"message": "Required"
}
]
}
Expected Behavior
I would expect multipart/form-data to work the same way as in previous version of undici.
Logs & Screenshots
Environment
NODE: v24.13.0
NPM: v11.10.1
Additional context
I can see same issue on never version 7.24.5.