Referee forgot to include his middle name on the declaration form

One of my referees just very kindly filled out the declaration form, but he left out his own middle name (his full name including middle name was on my online application).

Do I need to get him to fill out a new form with his full name or will his first and surname be fine for this?

I don’t want to get declined for some tiny technicality!

Applicants are not declined for minor errors. If you don't feel comfortable about this you could add an explanatory note with your documents explaining the facts - or if straightforward get referee to fill a new form.