Options traders are starting to pay up for crash protection, according to a recent note from Goldman Sachs. The question is whether that points to a heightened chance of a major correction.

"Long-dated crash put protection costs on the [ ] have more than doubled over the past 9 months," a Goldman Sachs options research team led by John Marshall wrote. "We believe it is an important development to watch as it implies investors are increasingly concerned about downside risk even as U.S. equities trade near all-time highs."

Specifically, the options that have more than doubled in value are 55 percent out-of-the-money puts that expire in five years. That is to say, in order for these derivatives to pay off come expiration, the S&P would have to lose more than half its value over the next five years.

The Goldman team notes that the increased risk of a catastrophic event implied by these put prices are not reflected in the credit markets—but that doesn't put their minds at ease.

"We see reason for concern as put prices were up a similar amount in 2007 ahead of the financial crisis, diverging from credit and equity at that time as well."

Stacey Gilbert, head of derivatives strategy with Susquehanna, sees further hints of concern in options that are merely playing for a correction, rather than a catastrophe.

"Where we've seen the primary focus has been the S&P June 1,800- to the 1,850-strike puts," she said, referring to trades that are playing for downside of more than 10 percent.

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Investors are "using these as an opportunity to buy insurance buy protection—not anticipating that there's a crash, but certainly wanting to be prepared in case there is."