Type Error: response2.headers.all is not a function

[markgeorgebg]

Hi

I have started getting the error "Type Error: response2.headers.all is not a function" on all my mocks. They were working fine, but now they are all broken because of this. I have the exact same setup on another repo and it is working and has been working for a long time. Has anyone had this issue before and found a resolution?

I am running an older version of MSW (1.2.1) but am not in a position to upgrade at this time.

Any help appreciated.
Thanks

[harrinsonmb]

Hello @markgeorgebg,

I was having the same problem and noticed that the .all() method was removed from headers-polyfill since version 3.3.0. So I decided to install an older version as a development dependency and it seems to work fine now.

npm i headers-polyfill@3.2.5 -D

I hope it works for you too.

Greetings!

[markgeorgebg]

Hey - this worked, thanks for your help - really helped me out of a spot!

[krzotki]

I also had this issue with configuring new repo, keeping the same setup. In my case the issue was with yarn.lock file - it was generated from scratch after installing deps, but it should've also been copied from the old repo.

[daniellizik]

i saw response3.headers.all is not a function but the polyfill did the trick, thanks!

node v16.4.2 (yeah i know...)

axios: 1.7.4
msw:  1.1.0
vitest: 0.29.7
vite: 4.5.5

[GabrielCastilhoV]

✅ Fix: Change msw from "1.2.2" to "^1.2.2"

If you're facing issues with MSW, a simple fix that worked for me was updating the version in package.json

from:

"msw": "1.2.2"

to:

"msw": "^1.2.2"

Using a fixed version ("1.2.2") locks you to that exact release, which may include bugs. Adding the caret (^) allows patch/minor updates (e.g., 1.2.3, 1.3.x) that include important fixes — and that alone resolved the issue in my case.