In wordpress I have a post with url https://www.example.com/article.html

I renamed its permalink to https://www.example.com/article-new.html

Now if I open old url https://www.example.com/article.html then it auto 301 redirects to https://www.example.com/article-new.html
due to wordpress built-in feature by default.

However I want to show 404 when someone tries to open https://www.example.com/article.html

I tried putting this in htaccess but it gave 500 server error instead:

RewriteEngine On
Redirect 404 /article.html

Please advice.