Cannot make one-to-one relationship. Underscore isn't recognized

Hi, I have tried to make one-to-one relationships in models but there’s a bug apparently.
I write [ref: _] but it displays the following exception
Expected " " or >,_ or < but “_” found.

Hi @jorguerra, i’m Khoa from the dbdiagram team, thank you for your feedback on the dbdiagram.
We support one-to-one relationship with the following syntax: