MetroCard vending machines this Saturday morning will be taking cold hard cash as the system's software gets an upgrade.

Riders will be unable to purchase a MetroCard from a vending machine with their credit or debit card during the upgrade, which will be done from 1 a.m. to 9:30 a.m. This affects every machine in the transit system, including the PATH stations and the JFK AirTrain.

An MTA spokeswoman said the software upgrade is part of routine maintenance for the fare-payment system.