DES MOINES, Iowa (AP) — Governor Terry Branstad has suspended rules limiting the work hour of truck drivers who haul propane. Branstad announce his action Wednesday evening. It’s effective Thursday and will continue through January 2nd.

Branstad signed a proclamation saying the suspension of work rules is necessary because of a shortage of propane. That’s due in part due to a late harvest that caused demand in the fall for the fuel, which is used by farmers to dry crops. Demand for propane is strong throughout the state, leading to some shortages.

Drivers must still abide by standard rules and can’t drive if they’re ill or overly sleepy.