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 ('87c035c9d97cb3eb6d0b8dd2a5e4e225', -1, 1539858189, 1539858189, '36c60f14', 1, 0, 0)

Line : 187
File : sessions.php