phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 'session_user_id'

INSERT INTO forum_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('7a6a6d852cdb843fab444c61d7adf3d9', -1, 1540046999, 1540046999, '36e09618', 15, 0, 0)

Line : 187
File : sessions.php