Urxvt: how to increase the amount of lines I can scroll back?

In other terminal emulators you can usually control the amounts of lines you can scroll back, but it seems it's a fixed amount in Urxvt. I thought the "saveLines" option controlled that but I tried changing it to a higher amount to no avail, the amount of lines displayed doesn't change no matter the amount. Is there any way to increase the amount of lines I can scroll back?