Shares of Straight Path soared nearly 22 percent Wednesday after the company announced its mystery bidder submitted a revised acquisition offer amounting to $2.3 billion.

According to Straight Path, the unnamed “multi-national telecommunications company” upped its previous bid of $104.64 per share (or $1.8 billion total) to $135.96 per share.

The bid comes as part of an effort to displace AT&T as heir-apparent to Straight Path’s millimeter wave spectrum. The carrier last month announced plans to scoop up Straight Path for $1.6 billion, or $95.63 per share. But soon after the offer was made, rumors began to swirl that a competitor – named by Reuters as Verizon – was sniffing around Straight Path as well.

At the end of April, Straight Path confirmed it had received a “superior proposal” from an anonymous party. AT&T was given five business days to respond (which would have been Tuesday, May 2), but no reports as to what counter offer the carrier made – if any – have surfaced.

AT&T has three business days to match or exceed the latest $2.3 billion offer, Straight Path said. If it doesn’t and Straight Path decides to jump ship for the higher bid, the spectrum company will have to pay a $38 million termination fee. Straight Path, though, has indicated its mystery bidder has agreed to pay the termination fee.

Straight Path currently holds 735 millimeter wave licenses in the 28 GHz and 39 GHz bands, which amount to an average of 620 MHz in the top 30 U.S. markets. The holdings represent about 95 percent of the commercially available 39 GHz spectrum licenses, CEO Davidi Jonas has said previously. Its 28 GHz airwaves also blanket key markets like New York and San Francisco, he said.

Back in January, the FCC gave the company 12 months to unload its spectrum assets as part of a settlement. More on that can be found here.