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) VALUES ('2f7b85c706da34f984d1342dac3980ae', -1, 1412238163, 1412238163, '6b15a3a7', -1, 0)

Line : 158
File : sessions.php