Belarus brought Great Britain's three-game winning streak to a halt on Sunday at the U20 European Championship Division B in Bulgaria.
Vitali Liutych poured in 21 points to lead Belarus to a 69-61 Group C triumph - their first victory at the big event in Sofia.
Despite the victory, Belarus have no chance of advancing to the Second Round.
Great Britain had already punched their ticket to the next stage before Sunday and are assured of finishing first in the group.
Beaten by Croatia and Denmark in their first two games, Belarus took a 34-33 lead at the Universiada Hall to half-time after two Liutych free-throws.
The Brits pulled level at 37-37 after the restart but at the end of the frame, Aliaksandr Semianiuk and Liutych connected from behind the arc to put Belarus in front, 52-43.
The advantage ballooned to 13 early in the fourth quarter after a dunk by Liutych and then increased to 14 when Semianiuk drilled another three-ball.
Once Belarus had the wind in their sails, Britain couldn't stop them.
When Robertas Ruzgatis made a lay-up with 3:22 to go, Belarus had their biggest lead of the game at 67-51 and there was definitely no way back for Britain.
Henadziy Zakhar weighed in with 12 points, nine rebounds and six steals for Belarus.
Semianiuk also finished with 10 points and eight boards.
Onyejebolise Chuku had 13 points and 13 rebounds for Britain and Ali Fraser led the team in scoring with 16 points.
The Brits played without leading scorer Devon Van Oostrum.
In a thrilling Group C encounter, Portugal edged Denmark, 74-73, with Rafael Wildner scoring 24 points for the winners.
Miguel Cardoso split two free-throws with 17 seconds remaining to put the Portuguese on top by a point.
The Danes had the last shot but Philip Hertz missed with an attempt from long range at the death.
On Monday, Denmark (1-2) will face Croatia (2-1) and Portugal (1-2) will go up against Belarus.
In Group B, the Netherlands were no match for Belgium.
Obasohan Ojomoh had another fine game for the Belgians with 21 points as they rolled to a 77-33 victory - their third in four games.
The result has assured Poland and Belgium of advancing to the Second Round.
Belgium opened up a 15-8 lead at the end of the first quarter and then put the result beyond doubt in the second when they outscored them, 26-3.
The Netherlands fell to 1-2.
Sunday's other game was a Group B clash between Luxembourg and F.Y.R. of Macedonia.
Gorjan Markovski had 26 points and 19 rebounds as F.Y.R. of Macedonia won convincingly, 87-68, for their first triumph in three games.
The team from the Balkans stormed into a 19-7 lead by the end of the first quarter and cruised to victory.
Luxembourg crashed to their third straight defeat.