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 ('7a4b6e45c1a892d5d50da53a94d4a152', -1, 1371691872, 1371691872, '36f2e90b', -1, 0, 0)

Line : 173
File : sessions.php