Error updating sessions table

DEBUG MODE

SQL Error : 1062 Duplicate entry 'viewtopic.php?download=17786&f=39&t=1229&_f_=39x&_t_=1229x' for key 'session_page'

UPDATE phpbb_sessions SET session_time = 1788985999, session_start = 1788985999, session_page = 'viewtopic.php?download=17786&f=39&t=1229&_f_=39x&_t_=1229x' WHERE session_id = 'bee14f2ca7d02822b0451f25a936a304'

Line : 556
File : sessions.php