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 ('612702fa6f1c6166ba2f876e8c8a2e29', -1, 1540131948, 1540131948, '36a285de', 1, 0, 0)

Line : 187
File : sessions.php