The non-partisan commission on presidential debates said there was indeed a problem with Donald Trump's microphone during Monday night's first presidential election debate.
The commission said on its website that "there were issues regarding Donald Trump's audio that affected the sound level in the debate hall".
There was no noticeable issue with the sound on television.
The Republican nominee complained about his microphone the morning after the debate, even suggesting he may have been sabotaged.
Rival Hillary Clinton had mocked the complaint, saying anybody who complains about a microphone "is not having a good night".