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 ('9d0d27274613919a956caf30c52ed375', -1, 1469462030, 1469462030, '36c6b355', 3, 0, 0)

Line : 187
File : sessions.php