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) VALUES ('8bc7a49c37b3ad3e949fbd6c5846171f', -1, 1467243603, 1467243603, '36a6b77c', 148, 0)

Line : 170
File : sessions.php