A comma (or the lack of one) in the wording of a state law could cost a Maine dairy $10 million. Oakhurst Dairy truck drivers sued the Portland, Maine-based company seeking unpaid overtime wages.

Driver Chris O’Connor was making a delivery when a supermarket employee asked the Oakhurst Dairy driver how many hours he’d worked that week. When O’Connor answered him, estimating it was about 60 hours that week, the supermarket employee said something about overtime pay. O’Connor said he was salary and didn’t make overtime, and the surprised supermarket worker said that was illegal. O’Connor decided to check out the law. He consulted a lawyer who knew there were several exceptions regarding which workers in Maine were eligible for overtime. But while reading the state law, the lawyer noticed the lack of clarity due to a missing Oxford comma.

The law says that workers aren’t eligible for overtime pay if they’re involved in “the canning, processing, preserving, freezing, drying, marketing, storing, packing for shipment or distribution of: (1) Agricultural produce; (2) Meat and fish products; and (3) Perishable foods.”

There’s no Oxford comma, also called a serial comma, between shipment and or. The Oxford comma is used after the penultimate item in a list of three or more items, before ‘and’ or ‘or’ (for example: … an Italian painter, sculptor, and architect). In journalism circles, the Oxford comma is sometimes a bone of contention. Some writers use it only when clarification is necessary, others use it unfailingly. “My heroes are my parents, Superman and Wonder Woman.” I don’t think any of us would believe that some guy’s parents are actually Superman and Wonder Woman, but an Oxford comma would clear things up. Enough with the grammar lesson.

The lack of the Oxford comma makes the Maine overtime law unclear, claimed attorney Jeffery Young, who asked, is it packing for shipment or distribution, or is it packing for shipment, or distribution? This prompted Young to file a $10 million class action suit on behalf of 75 Oakhurst Dairy drivers.

A district court ruled in favor of Oakhurst, and the court argued the law was clearly intended to count distribution as a distinct, exempt activity, meaning the drivers had no legal right to overtime wages, according to a story in the Bangor Daily News.

But in March, the U.S. First Circuit Court of Appeals overturned the district court’s decision, arguing that the passage is too ambiguous, so the state’s wage laws must be “construed liberally” by the courts, giving more credence to the drivers’ interpretation of the passage, the Bangor Daily News reports.

This case is not closed. It’s uncertain how the rest of this lawsuit will play out in the courts, but the drivers’ attorney told NPR that he sees the humor in the situation. During a broadcast of “All Things Considered” Young quipped, “My first boss always used to say to us, common sense ain’t so common. So my summary of this case is, comma sense ain’t so common.”

Details, even one comma, can make an enormous difference. If attention to detail is not your particular strength, make sure someone in your operation fits that description and can review documents and rulebooks.