Bets are starting to pile up in distant corners of the U.S. options market that tomorrow’s U.K. referendum will ignite massive losses in stocks.

In the last four days, open interest for deep out of the money puts on the S&P 500 that mature on Friday have increased 1100%.

These options will only pay off if the S&P plunges 20% or more on Friday.. and are the second most held of all weeklies...

As Bloomberg reports, "It's a black swan type of put," said Steve Sosnick of Timber Hill LLC. "It's very possible there will be an extreme result, and people like to have insurance against a low-probability, high-outcome event."

In case you're interested - these lottery tickets are trading for 5c.