Error 404 on `npm deprecate` of an alpha version that exists

Hello,

I’m trying to automatically deprecate versions of npm packages. When I run this command:

npm deprecate semantic-release-npm-deprecate-old-versions@"1.2.0-alpha.1" "Deprecated in favor of 1.2.0-beta.1" --json

I get a 404 error:

{
  "error": {
    "code": "E404",
    "summary": "Not Found - PUT https://registry.npmjs.org/semantic-release-npm-deprecate-old-versions - Not found",
    "detail": "\n 'semantic-release-npm-deprecate-old-versions@1.2.0-alpha.1' is not in the npm registry.\nYou should bug the author to publish it (or use the name yourself!)\n\nNote that you can also install from a\ntarball, folder, http url, or git url."
  }
}

But this package name and this version both exist as you can see here: semantic-release-npm-deprecate-old-versions - npm

And I’m also connected to my account, that has the right to administrate this package.

This command seems to work with regular versions (I could run it on the version 1.1.6 with success), but it fails with the version alpha.

It seems to be a problem with the npm repository. Do you have an idea why it fails?