phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 'session_user_id'

INSERT INTO r2ok_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('35ad68f861d6e36c20abe52f5915fec0', -1, 1524207193, 1524207193, '3650082c', 15, 0, 0)

Line : 187
File : sessions.php