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 ('322e8f8e418d70bccad3fdd33f364962', -1, 1472493294, 1472493294, '36e0717d', -1, 0, 0)

Line : 187
File : sessions.php