Marathon Digital mines invalid block due to bug

Marathon’s error occurred at block height 809478, and Foundry ended up snagging the reward


Elisabeth Coelfen/Shutterstock modified by Blockworks


Even the largest miners and mining pools can occasionally make mistakes, as evidenced by Marathon Digital’s error early Wednesday morning.

The publicly traded company mined an invalid block. This means that Marathon submitted a block — which is made up of 2,000 transactions on average — that the rest of the network rejected because it didn’t align with common protocol. 

If the other nodes on the network detect an invalid transaction within the block, they can come together to reject using the consensus mechanism built into Bitcoin. 

Jameson Lopp, a bitcoin engineer and chief technology officer and co-founder of Casa, told Blockworks that Marathon mining an incorrect block doesn’t present a problem for the network. It’s more just a matter of forfeited profit. 

“It’s not a problem for the network, it’s only a problem for the money because [Marathon] gave up over $100k in revenue,” Lopp said. 

The issue with block 809478 was first flagged by X user @0xB10C, but BitMex Research pinpointed the error: Marathon misplaced two transactions within said block. This misordering led to the block’s rejection by other network participants.

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Marathon confirmed what happened on Wednesday afternoon in a post on X, formerly Twitter. The company chalked the mistake up to an unforeseen bug that compromised its development pool, not its main production pool. 

“We utilize a small portion of our hash rate to experiment with our development pool and research potential methods to optimize our operations,” the company wrote. “The error was the result of an unanticipated bug that came from one of our experiments.”

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The incident, it further explained, was “unintended” and not meant to alter the inherent rules governing Bitcoin Core, the original and most widely adopted software client used to operate nodes on the Bitcoin network.

Marathon also took this opportunity to hype up its view that Bitcoin is secure, saying that this “underscores the robust security of the Bitcoin network, which rejected and rectified the anomaly.”

This isn’t something that’s only happened to Marathon, however. 

BitMex Research flagged an invalid block seemingly mined by AntPool in July 2019. A similar occurrence was noted in April 2023 involving f2pool.

According to multiple blockchain explorers, Foundry was the one to ultimately mine block 809478 correctly.

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