Newcastle suffered their first pre-season loss in the sweltering German heat - with the Magpies edged out late on by Bundesliga side Mainz.
Rafa Benitez's men fell behind early on when Pablo De Blasis played a ball in behind a static Paul Dummett, who was captain, for Levin Oztunali to slot home past Karl Darlow for the opener.
It took United until the 65th minute to get back on terms and it was through an unlikely source, as well as in an unlikely fashion.
Jesus Gamez's snapshot, after sharp work by Christian Atsu down the right, took a heavy deflection off a home defender before hitting the post and was then diverted home by the Mainz keeper.
Freddie Woodman was thrown on from the bench and was called into action almost instantly, enhancing his growing reputation further with a remarkable one-handed reaction stop to prevent United going behind.
But on 84 minutes he could do little about Mainz's winner. A ball out to right caught Javier Manquillo out of position and allowed former Middlesbrough forward Viktor Fischer the time and space to slot home from 12 yards.
Benitez handed a debut to recent signing Mikel Merino, who replaced Florian Lejeune in the 79th minute of the game.