phpBB : Critical Error

Error creating new session

DEBUG MODE

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

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('8cc4cebb94eeb3405b1b7c4287b9c236', -1, 1432581335, 1432581335, '369ffa6e', 5, 0, 0)

Line : 189
File : sessions.php