Need Help with CMS-1500 - payer denies claim because client's gender is X, which is not an option on the form to submit

Hello! 

I have a client who is non-binary and when I look up their EOB through Excellus BCBS, it states that the gender of the client is "X or not provided." For these reasons I had a claim denied, as the CMS-1500 only has options for either M or F. 

Can anyone assist me with this?