# (Dev contribution) Unable to activate the theme "casper"

**URL:** <https://forum.ghost.org/t/dev-contribution-unable-to-activate-the-theme-casper/38172>\
**Category:** Developer help\
**Created:** [May 1, 2023, 1:05pm UTC](https://forum.ghost.org/t/dev-contribution-unable-to-activate-the-theme-casper/38172 "2023-05-01T13:05:56Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Mysterious-Dev](https://sea1.discourse-cdn.com/flex015/user_avatar/forum.ghost.org/mysterious-dev/32/24232_2.png) [@Mysterious-Dev](https://forum.ghost.org/u/Mysterious-Dev)\
**Post date:** [May 1, 2023, 1:05pm UTC](https://forum.ghost.org/t/dev-contribution-unable-to-activate-the-theme-casper/38172/1 "2023-05-01T13:05:56Z")

</div>

Hello ! When I follow the developper setup guide to contribute to Ghost, I have this error when I try to run `yarn dev`

I’m on a W11 (22h2) and I use NodeJS 16.19.1.

> **[Ghost Docs](https://ghost.org/docs/install/source/)**
>
> Everything you need to know about working with the Ghost professional publishing platform.

````auto
[ghost] [2023-05-01 13:01:17] ERROR Unable to activate the theme "casper".
[ghost]
[ghost] Unable to activate the theme "casper".
[ghost]
[ghost] Error ID:
[ghost] 42ad8920-e820-11ed-b59b-f5265c549dc6
[ghost]
[ghost] Error Code:
[ghost] ENOENT
[ghost]
[ghost] ----------------------------------------
[ghost]
[ghost] Error: ENOENT: no such file or directory, copyfile 'C:\Github\Ghost\ghost\core\core\frontend\src\admin-auth\index.html' -> 'C:\Github\Ghost\ghost\core\content\public\admin-auth\index.html'
[ghost] at Bridge.activateTheme (C:\Github\Ghost\ghost\core\core\bridge.js:76:27)
```
````

---

<div class="post-metadata">

**Author:** ![Mysterious-Dev](https://sea1.discourse-cdn.com/flex015/user_avatar/forum.ghost.org/mysterious-dev/32/24232_2.png) [@Mysterious-Dev](https://forum.ghost.org/u/Mysterious-Dev)\
**Post date:** [May 11, 2023, 3:45pm UTC](https://forum.ghost.org/t/dev-contribution-unable-to-activate-the-theme-casper/38172/2 "2023-05-11T15:45:40Z")

</div>

Hey, to have some help, should I switch to WSL (Windows Subsystem for Linux) or something else ?