FORTUNE — Mark Zuckerberg, Facebook’s founder, just wanted a little peace and quiet at home. To get it, he bought out all his neighbors in Palo Alto, Calif. – four lots total – for $43 million. Problem solved? Not really.

A developer who had an eye on one of the properties has now sued Zuckerberg for breach of contract, the San Jose Mercury News reported. He has accused Zuckerberg of failing to keep his promise to introduce him to other wealthy people who might want to buy homes.

Mircea Voskerician, the developer, had made an offer to buy a property next door to Zuckerberg’s and build a mansion there. But after learning of the plans, Zuckerberg paid Voskerician $1.7 million to pull out of the deal so he could buy the lot instead, according to the Mercury News.

“Zuckerberg stated he did not want construction in his backyard for 14 months and told Voskerician that he would refer him business and make him introductions if, in exchange, Voskerician would help him secure his privacy,” the lawsuit said.

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Zuckerberg paid $4.8 million for the house, the same price that Voskerician had originally offered. In buying the other neighboring homes, Zuckerberg paid from $10.5 million to $14.5 million.

“Here’s this guy who built his business on connections and relationships, and all he had to do was make some introductions, but he blew my client off,” David Draper, an attorney for Voskerician, told the Mercury News.

Zuckerberg’s promise to make introductions wasn’t in the final contract, Draper acknowledged. But several people who attended the meeting between Zuckerberg and Voskerician witnessed the pledge, he said.

Zuckerberg’s attorney told the Mercury News that the lawsuit was without merit. The suit was filed last month in Santa Clara Superior Court.