Boy, did this couple make a costly mistake.

An expectant mom and dad from Nebraska that set off an exploding target while revealing the gender of their baby has been fined $1,000 because they didn't have a permit.

Jon and Ashley Sterkel wanted to do something different while announcing the news on Facebook, so they used the targets which settled into a cloud of blue dust -- blue for boy, of course.

The explosion was so jarring that people from three miles away in the town of Scottsbluff called police. Jon got wind of that and called authorities to tell them what happened.

Honesty may be the best policy, but it's not best for the couple's bank account: cops ticketed him for setting off the explosive without a permit, which carries a punishment of up to a year behind bars and a $1,000 fine.

Jon has certainly learned his lesson. "People need to follow the proper protocol," he said. "We never knew, and we've shot these for years. If you can go to a store and buy it, how in the world can you know it's illegal?"

The baby boy, by the way, is due in June.