Traders seem to be pinning expectations for oil prices to one specific number now that crude has staged an impressive comeback this year.



In the past month, WTI crude oil has rallied more than 20 percent, taking the commodity into positive territory for the year. But technician Craig Johnson of Piper Jaffray said he's waiting for crude to hit $40 before changing his bearish tune.



"It's going to take a close above $40 to reverse a long-term downtrend we've seen," Johnson said Friday on CNBC's "Power Lunch." "At this point in time, I'm skeptical."



Johnson isn't the only one setting store by the $40 level in crude oil. Options that allow their owners to buy crude oil for $40 or above have seen notably more buyers and sellers compared with all other strike prices. Calls that expire in May and June have higher levels of open interest at $40 than at any other level. On Monday, call contracts that expire in April saw the highest trading volume in the $40 strike.



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Before crude oil reaches that key level, Johnson said he foresees another wave of pain for the commodity.