With bitcoin rallying above $55,000 for the first time since May, cryptocurrency miners are holding onto their newly minted currencies to bolster their balance sheets.

Recent monthly production updates from crypto miners such as Riot Blockchain and Marathon Digital Holdings show that they have kept their mined bitcoins during September, when prices hovered around $40,000.

Riot Blockhain, the Castle Rock, Colo.-based miner, said in a statement Wednesday that as of Sept. 30, it holds 3,534 bitcoins, an increase of 406 bitcoins from August. Riot’s share price rose as much as 6.5% on Wednesday, before paring gains to close the trading session up about 1%.

Read more: Crypto Miners Marathon Digital, Hut 8 Rally as Bitcoin Tops $50,000

Meanwhile, Riot’s competitor, Marathon Digital Holdings, said on Oct. 4 that it now holds 7,035 bitcoins on its balance sheet, after producing 340.6 new bitcoins in September. It previously said the company held 6,695 bitcoins in August. Marathon’s stock was up 4.8% on Wednesday.

Adding to the trend, on Oct. 4, Canadian Hut 8 Mining Corp. also reported that all of its self-mined bitcoins were deposited into custody, which is consistent with the company’s strategy to “hodl” its mined digital currency. “We are thrilled with our current amount of bitcoin held in reserve as well as being ahead of schedule on our commitment to the market to have over 5,000 self-mined bitcoin by end of Q4,” said Jaime Leverton, CEO of Hut 8, in a statement.

The strategy of holding onto the digital currency is that in a bull run, doing so is likely to help miners’ balance sheets and bolster investors’ bullish sentiment on the overall sector. The miners are already enjoying continued profitability, as the prices for bitcoin have recovered from their recent decline and climbed about 88% this year.

Riot’s share price has climbed about 57% this year, while Marathon has jumped 254% and Hut 8 has risen 232%.

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