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 ('78326947c2e39ed5a0173b3f895a565d', -1, 1540170858, 1540170858, '369c27f5', 3, 0, 0)

Line : 187
File : sessions.php