Space Exploration Technologies Corp (NASDAQ:SPCX) shares remained below their IPO price on Thursday after closing at $131 as economist Peter Schiff warned that upcoming share lockup expirations could further pressure the stock by significantly expanding its tradable float.

Schiff Flags Lockup Expiration Risk Schiff said SpaceX had fallen as low as $126.25 in extended trading, adding that the stock's recent decline came before the company's insider lockup expirations and that its tradable float could expand eightfold by the end of the year as restrictions on insider sales are lifted.

The stock has retreated nearly 44% from its record high of $225.64, with Schiff saying that the stock was "coming back down to earth." "Houston, we have a problem!" Schiff said, adding that the expected increase in shares available for trading could create additional pressure on the stock. $SPCX is coming back down to earth in after-hours trading.

It’s down 3.7% to $126.25.

That’s 6.5% below its IPO price and 44% below its high.