phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 2

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('88ed1eade4cd3caf282a074bd27771b4', -1, 1414745677, 1414745677, '36eb1d6e', 29, 0, 0)

Line : 187
File : sessions.php