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 ('cf03ba83195987c5104d2b00b3e0f5a9', -1, 1540128577, 1540128577, '369c27f5', 3, 0, 0)

Line : 187
File : sessions.php