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 ('ec71e64099b7e0ed310d2b6e16d217a2', -1, 1539699920, 1539699920, '36e09618', 7, 0, 0)

Line : 187
File : sessions.php