Stephen Henderson has returned to Fratton Park to complete Pompey's deadline day work.
The goalkeeper has joined the Blues in a loan deal from Nottingham Forest until the end of the season.
He will now compete with league ever-present Luke McGee for Pompey's number-one spot.
The 29-year-old previously had a spell under Steve Cotterill and then Michael Appleton during the 2011-12 campaign, making 27 appearances.
Henderson has since turned out for West Ham, Ipswich, Bournemouth, Charlton and Forest.
He becomes Pompey's fourth and final January transfer window recruit, all loans.