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 ('c2d33c8a6ce6784a0a9247b9736e4431', -1, 1397717172, 1397717172, '6ca2d4e2', 45, 0, 0)

Line : 187
File : sessions.php