301 redirect for a URL with spaces

Question:
I transferred an old html site for a client and created redirects for pages that no longer exist. A few of them had spaces in the URL. when I enter the URL into the redirect manager, example: /old%20page.htm - as soon I exit the field, it converts to /old page.htm and presents a warning that my URL cannot contain spaces. How can get it to stop changing my entry?

Product:
Wix Dashboard - Redirect Manager

What are you trying to achieve:
I transferred an old html site for a client and created redirects for pages that no longer exist. A few of them had spaces in the URL. when I enter the URL into the redirect manager, example: /old%20page.htm - as soon I exit the field, it converts to /old page.htm and presents a warning that my URL cannot contain spaces. How can get it to stop changing my entry?

What have you already tried:
I’ve only tried replacing the spaces with “%20”. I’m not aware of any other solution.

I’m having the same problem. Would love to find a solution!