Charlton midfielder Dale Stephens has joined Brighton for an undisclosed fee.
The 24-year-old, who was out of contract in the summer, has penned a three-and-a-half-year deal at the Amex.
A club statement read: "Following the takeover of Charlton by Roland Duchatelet in early January, talks began with Stephens' representatives over taking up the option of 12-month extension to keep him at The Valley.
"However, with the prospect of losing him for nothing at the end of his current deal, once an acceptable offer was received from Brighton the decision was reluctantly made to allow discussions over a move to take place.
"The club will now look to use the funds received from the transfer to help secure suitable reinforcements to the playing squad before the end of the January transfer window."
Manager Chris Powell added: "Dale is showing himself to be the player we always envisaged.
"He did in League One and he has shown in spades this season what he is about.
"I really like him and wish him well."