Youssoufa Moukoko became the youngest goalscorer in Bundesliga history on Friday, but he couldn't prevent Borussia Dortmund from slumping to a 2-1 loss at Union Berlin.
Moukoko had struck the post in the first half from a Raphael Guerreiro pass but made no mistake with a similar chance on the hour, firing a left-foot shot high beyond home keeper Andreas Luthe.
The Cameroon-born German youth international scored at age 16 years 28 days, massively cutting the record held by Bayer Leverkusen's Florian Wirtz of 17 years 34 days.
Moukoko became eligible for Dortmund's first team on his 16th birthday and subsequently became the youngest-ever player in the Bundesliga and Champions League.
His goal cancelled out Taiwo Awoniyi's 57th-minute opener but Marvin Friedrich's late header handed interim Dortmund coach Edin Terzic a first defeat.
"We have to congratulate the young 16-year-old on his goal. It's something special," Union captain Christopher Trimmel said.
"We're on the right path," added Trimmel. "Many people said we'd struggle with the absences of (injured forwards) Max Kruse and Joel Pohjanpalo, but we're a team. It's fun."
Dortmund are fourth in the table, six points behind leaders Bayer Leverkusen who host champions Bayern Munich on Saturday.
Union Berlin are an impressive fifth and just one point behind Dortmund going into the winter break.