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 ('9b2a00fd526803c410a9074e6ca6f25a', -1, 1529398373, 1529398373, '36e0ebb7', 39, 0, 0)

Line : 187
File : sessions.php