Composer.json requires wrong version of Captcha

If I'm not mistaken, the version required in the composer.json is wrong, isn't it? Upon trying to update with composer, I get this error message:

Your requirements could not be resolved to an installable set of packages.

Problem 1
- The requested package drupal/captcha ~8.0 exists as drupal/captcha[dev-1.x, 1.x-dev, 1.0.0-beta1, 1.0.0-alpha1, 1.0.0-alpha0] but these are rejected by your constraint.

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I don't know if the problem is that Captcha is naming its versions strangely, or what's going on. The current version of Captcha is 8.x-1.0-beta1, clearly stated on the project page, but composer seems to think it is 1.0.0-beta1. When I changed reCaptcha's composer.json to require Captcha at 1.0.0-beta1, it works fine.