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 ('39895aa8b3224e3d95de00b6c7f023af', -1, 1540352646, 1540352646, '369ed0bd', -1, 0, 0)

Line : 187
File : sessions.php