The spokesman said the maintenance was timed to not coincide with any live sports events - though it left an NZME staffer who was trying to subscribe to the service frustrated.
The Rugby World Cup kicks off in 111 days.
Spark has stressed that its service has been in a "beta" or test phase that was always going to involve ironing out a few bugs - and that it has worked smoothly most of the time so far.
Still, users have taken to social media to sound-off about bugs that have affected Spark Sport Formula One and hockey coverage at times.
Spark also copped flak after saying not all people in rural areas have good enough broadband for Spark Sport.
The telco is easying the path by allowing pubs and clubs a Spark Sport subscription at a household rather than commercial rate, and by making all the All Blacks pool games, plus the semis and final, available through free-to-air partner TVNZ. The pool games will screen on a one-hour delay.
TVNZ will also screen the opener, plus the All Blacks presumed quarter-final on a one-hour delay.