Millwall have signed Ipswich goalkeeper Bartosz Bialkowski on a season-long loan deal, while Jason McCarthy has also joined from Wycombe.
Bialkowski, 32, has been at Portman Road since the summer of 2014, making 178 appearances for the Tractor Boys.
Defender McCarthy, 23, joins for an undisclosed fee having scored two goals in 49 games last season.
Meanwhile, Millwall forward Fred Onyedinma, 22, has re-signed for Wycombe, also for an undisclosed fee.
Onyedinma scored four goals in 21 league appearances in a five-month loan spell last season, having spent the second half of the 2014-15 campaign with Wycombe - helping them reach the League Two play-off final.
Both he and McCarthy have signed "long-term" contracts with their respective new clubs.
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