W3C Validation for Twitter

I actually do have the same problem / question…

Bad value twitter:card for attribute name on element meta: Keyword twitter:card is not registered.
Bad value twitter:site for attribute name on element meta: Keyword twitter:site is not registered.
Bad value twitter:creator for attribute name on element meta: Keyword twitter:creator is not registered.
Bad value twitter:description for attribute name on element meta: Keyword twitter:description is not registered.

12 Errors resulting on using the meta card twitter option… ??

If https://sitevalidator.com/top100/errors/fix/bad-value-twitter-card-for-attribute-name-on-element-meta-keyword-twitter-card-is-not-registered is true then maybe Yoast should use that instead?

It’s true. Facebook uses the same.
To solve the issue:

1. navigate to the following directory within your wordpress installation:
   /wp-content/plugins/wordpress-seo/frontend
2. In that directory, open the file called “class-twitter.php”
3. search for the text “meta name” (without quotes) and change all occurrences to “meta property”

Issue solved.

But I hope Yoast makes the change also or we will loose the change after plugin update.