Bypassing temperature drop safety feature

Because I completely winterize my summer home in the winter when I am not there until spring, I am able to completely turn off the furnace (remotely via the Nest device) without the risk of freezing pipes. I just recently realized that the nest device (even in off mode) will automatically switch to a safety mode, not allowing the temp in the house to drop below 39 degrees. Does anyone know of a way to bypass this feature so that when I set it to off- it stays off?