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 ('3a19093ee4498c5f6a9c21aba38a5497', -1, 1516785434, 1516785434, '36ea414e', 1, 0, 0)

Line : 189
File : sessions.php