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 ('ae4beb3c37490567d1a5f9748b5d6695', -1, 1513621969, 1513621969, '3652385f', 0, 0, 0)

Line : 193
File : sessions.php