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 ('71f02a2a6b14b69b1bb8b9cd9db82d1e', -1, 1529334855, 1529334855, '36e05573', 36, 0, 0)

Line : 187
File : sessions.php