Nasdaq OMX  has temporarily suspended its so-called penny stock requirement for listed companies, some of which have seen their share prices plunge in the recent market drop, the exchange operator confirmed on Monday.

Nasdaq made the regulatory request on Thursday last week and the suspension went into effect Friday, a spokeswoman told Reuters.

The requirement the shares of listed companies stay above $1 will be suspended until Jan. 16.

Usually, public companies listed on the Nasdaq Stock Market that fall below $1, on average for 30 days, are warned they must boost their share price within six months, or face delisting.

The spokeswoman did not immediately say why Nasdaq suspended its rule.

But the market operator suspended the penny stock requirement at least twice in the past, including shortly after the Sept. 11, 2001 attacks in the United States, to protect falling stocks from mass delistings.