Walta won six caps with the Finland senior side in 2024, grabbing an assist against England in the UEFA Nations League, before re-joining the U21 setup in March in preparation for the Euros.
However, the Finnish FA have now confirmed that Walta will play no part, due to an unspecified illness.
Central midfielder Walta has scored five times for Sirius in 12 Allsvenskan matches in 2025 as one of the side's most consistent performers in a difficult season so far. In his stead, Doni Arifi of KuPS has been called up.
The Little Eagle-Owls will play in the U21 Euros for just the second time, having lost all three group stage matches in the 2009 edition.
This time, they play their first Group D match against the Netherlands on Thursday, before a meeting with Ukraine on the 15th and then Denmark on the 18th. All three matches will be played at the Kosicka futbalova arena in Kosice.
Finland U21 squad
The Finland U21 squad for UEFA Under-21 Euro 2025 (players marked in bold have been capped at senior level):
Goalkeepers: 1 Lucas Bergstrom,12 Elmo Henriksson, 23 Roope Paunio
Defenders: 2 Rony Jansson, 3 Tomas Galvez, 5 Samuli Miettinen, 14 Kalle Wallius, 16 Dario Naamo, 21 Ville Koski, 22 Miska Ylitolva
Midfielders: 4 Matti Peltola, 6 Santeri Vaananen, 7 Naatan Skytta, 8 Adam Markhiev, 13 Niklas Pyyhtia, 15 Luka Hyrylainen, 20 Otso Liimatta
Forwards: 9 Teemu Hytonen, 10 Doni Arifi, 11 Casper Terho, 17 Juho Talvitie, 18 Topi Keskinen, 19 Oiva Jukkola
Follow every match at the 2025 UEFA European Under-21 Championship on Flashscore.