Using a magnifying glass, the listener had spotted that the text in Edith Cowan's speech - which is so microscopic it can't be seen my the naked eye - that the word 'responsibility' had been spelled wrong.
The speech reads:
'I stand here today in the unique position of being the first woman in an Australian parliament. It is a great responsibilty.'
The last 'i' in responsibility has been missed. Even more unusually, it's not just once, with the same mistake being repeated all the way down.
When asked by the radio host Eddie McGuire if he knew if it had simply been an honest error, the listener seemed to have some inside knowledge.
'Well, it was considered maybe to be a security issue, that maybe they did it on purpose, but it wasn't and they're withdrawing, well stopping distribution of the new $50 note apparently,' he said.
A Reserve Bank of Australia spokesperson said they were aware of the error.
'The spelling will be corrected at the next print run,' they said.
The new note was released in October 2018 with a range of security elements and features to help visually-impaired people distinguish between different denominations.