term name contextual filter separator

I am using the contextual filter: 'Content: Has taxonomy term ID' to parse a path: 'vocabulary/my_title'.
Validating the term by using Filter value type: 'Term name converted to term ID'

Here there is an option: 'Transform dashes in URL to spaces in term name filter values'. If I check this option and rewrite my url to: 'vocabulary/my-title' then everything works fine. The problem is I don't want to rewrite the paths to my nodes which I have set using patterns in URL aliases to use an underscore as the separator (as opposed to a dash).

My feature request is to be able to enter the character to be transformed into spaces for the filter or have the filter option use the setting from the pathauto module.

Thanks