Florida Gov. Charlie Crist Monday signed into law a bill requiring that all voting districts in the state replace most touch-screen electronic voting machines with optical scan machines.

The bill, sponsored by Crist, was passed by the state legislature earlier this month.

At the time, Crist said he filed the bill in response to experts that said touch-screen systems, also known as Direct Recording Electronic (DRE) machines, were vulnerable to hackers, were unreliable and made voters doubt their ballots were counted.