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) VALUES ('0bbf2963b5cab1194cf0d58e235d8d0f', -1, 1490328953, 1490328953, 'ac44417d', -8, 0)

Line : 158
File : sessions.php