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 ('ef78060c0fe95f164de5ecd6673397d7', -1, 1529905761, 1529905761, '36e11fbc', -9, 0, 0)

Line : 187
File : sessions.php