Want two authors listed as one author

My wife and I write books together, and self-publish on-line. We use Calibre to convert the stories to ePub and mobi formats.

If I enter our names as "Lehmann, Michelle and James", then Calibre converts our names into two authors, "Lehmann, Michelle" and "James". What I'd like is to keep it as one author, "Lehmann, Michelle and James".

I've gone into "tweaks" and tried to change:

authors_split_regex = '(?i),?\\s+(and|with)\\s+'

into:

authors_split_regex = '(?i),?\\s+(with)\\s+'

...which I feel is the right answer, but the change never saves. I make that change, exit Calibre, re-start, and then go back into Tweaks, and the original version of this value is there again.

If anyone could help me to either make this change, or find a way to work around it, I'd appreciate it. Thank-you.