Bitcoin, the world’s biggest digital currency, drifted back under $8,500 on Monday as weekend gains slowly faded. The broader digital-currency market fared even worse, with most virtual assets kicking off the week in decline.

After reaching a weekend high of $8,575.99, bitcoin has retreated and a single bitcoin BTCUSD, +0.64% was last worth $8,402.63, down 1.8% since Sunday’s levels at 5 p.m. Eastern Time on the Kraken exchange.

Despite the sluggish start to the week, some bulls remain unbowed. Rodrigo Marques, chief executive of Atlas Quantum, one of Brazil’s largest crypto trading platforms, said in an email to MarketWatch that the move under $8,000 was an interim low for bitcoin, adding that he expects bitcoin to reach $20,000 in six months, recapturing levels it hasn’t approached since December.

Read:A recent shift in Uranus means big things for cryptocurrencies

CFTC to publish guidance on virtual currencies

The Commodity Futures Trading Commission, or CFTC, will soon provide tighter guidance on the digital currency market. Speaking at the North American Securities Administrators Association Conference in Washington, Chairman Christopher Giancarlo said the agency will publish a staff advisory that will provide a framework to both exchanges and clearinghouses when listing derivative contracts based on digital assets.

“This advisory will reflect CFTC staff’s current thinking based on our growing experience with virtual currency derivatives. As new products are brought forth, staff will reevaluate and revisit the advisory, as necessary, to address any new and emerging issues,” said Giancarlo.

Read:The advent of bitcoin futures sparked the selloff from $20,000, says San Francisco Fed

What are altcoins and futures doing?

Altcoins, or digital assets other than bitcoin, stumbled out of the blocks Monday and continue to trade lower throughout the day. Ether ETHUSD, +0.24% is down 3.2% to $695.53, Bitcoin Cash BCHUSD, +1.50% has lost 5.7% to $1,225.80, Litecoin LTCUSD, +1.52% is off 4.1% at $134.42 and Ripple’s XRP coin XRPUSD, -0.38% last traded at 68 cents, down 4%.

Futures finished higher Monday after the spot rally over the weekend. The Cboe June contract US:XBTM8 finished Monday up 1.7% at $8,395, while the CME May contract US:BTCK8 closed up 1.8% at $8,375.

CryptoWatch:Check bitcoin and other cryptocurrency prices, performance and market capitalization—all on one dashboard