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 ('381e7022e56334b3ac7a9d80a07b0408', -1, 1472629699, 1472629699, '17148881', -1, 0, 0)

Line : 187
File : sessions.php