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 ('2e74e6e43e868976077f89a9bd6f0fe3', -1, 1529905666, 1529905666, '36e11fbc', 41, 0, 0)

Line : 187
File : sessions.php