Organisers of Monday's White House debate have confirmed Donald Trump's roundly mocked complaint that his microphone was defective.
The Commission on Presidential Debates said "there were issues regarding Donald Trump's audio".
After the forum in New York, the Republican candidate said his microphone was "terrible" and crackled.
The volume on the device was lower than that of Democratic nominee Hillary Clinton, he said.
Friday's brief statement by the independent commission said the unspecified problems had "affected the sound level in the debate hall".
After their battle of wits, Mrs Clinton had panned Mr Trump's debate performance, saying it had nothing to do with the audio.
"Anybody that complains about the microphone is not having a good night," she said.
Late-night comedians also ridiculed Mr Trump's mic gripe, with Trevor Noah of the Daily Show dismissing it as a lame excuse.
The presidential debate at Hofstra University was the first of three to take place before the end of October.
The next is scheduled for 9 October in St Louis, Missouri. The third is on 19 October in Las Vegas.