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 ('963003d0ea3443cde44e8a76f7060486', -1, 1540134788, 1540134788, '36a285de', 4, 0, 0)

Line : 187
File : sessions.php