Facebook’s initial public offering (IPO) was delayed by more than half an hour on Friday due to a glitch in NASDAQ’s IT systems, the stock exchange’s CEO Robert Greifeld said over the weekend.

Greifeld told reporters on a conference call that the fault was down to “poor design” in the exchange’s auction software, which it uses for IPOs, Bloomberg reports.

He said the glitch had not effected the performance of Facebook’s stock on its opening day, and that the IPO had been “successful”. The stock finished trading at $38.23, up just 23 cents from its opening price.

However, Greifeld admitted that NASDAQ was “humbly embarrassed by the software failure”.

The glitch echoes a similar incident that struclk BATS Global Markets,the company that operates the third largest stock exchange in the US, in March. The company attempted to float on its own exchange in March, but an IT glitch prevented shared including its own from being traded.

BATS Global Markets cancelled its IPO as a result.