Plaid Cymru must have hoped the title of its election manifesto - Ambition is Critical - captured the essence of one of Wales' most famous exports, the poet Dylan Thomas.
Launching the key document, it could not have known the embarrassment ahead.
It turns out the phrase it attributed to Thomas was the work of a slightly less celebrated poet - David Hughes.
Plaid said it had been told it was Thomas's work, and it will now correct the manifesto online.
The document sets out the party's policies for the assembly election on 5 May and makes direct reference to the quote being written by Dylan Thomas.
It reads: "Plaid's vision for what it describes as the next decade of delivery is reflected in the title of the document 'Ambition is Critical'.
"As Wales prepares in 2014 to mark a centenary since the birth of Dylan Thomas, his words have been adopted by Plaid as their guiding principle for both the manifesto and the next Welsh government."
But the phrase "ambition is critical" was the work of retired social worker David Hughes, 63. It also featured in the cult comedy Twin Town, starring Rhys Ifans.
'Magic of place'
He was one of three artists commissioned by Swansea council in 1992 to produce poems celebrating "the magic of place".
Mr Hughes said he was inspired to write in response to the phrase "the graveyard of ambition" - a phrase commonly attributed to Thomas but, once again, wrongly.
When told of Plaid's mistake by the BBC Wales News website, Mr Hughes said: "I'm not surprised. It's amusing and I suppose I'm flattered.
But he added: "They're not the only ones. The quote is widely attributed to Dylan Thomas on the internet."
Meanwhile, a Swansea council spokesman confirmed the line was written by Mr Hughes, not Thomas.
Swansea University creative writing lecturer Nigel Jenkins said: "Ambition is critical is a splendid slogan for Plaid Cymru to have chosen for its election manifesto, but, in attributing these words to Dylan Thomas, Plaid leader Ieuan Wyn Jones is launching a new urban myth on the back of a hoary old one.
"David's micro-poem was a response to that infamous Swansea dead-hand which describes the city as 'the graveyard of ambition' - which for years has been routinely, and wrongly, attributed to Dylan Thomas.
"Dylan Thomas specialists at Swansea University inform me that there is no evidence that he ever wrote or spoke those words," said Mr Jenkins.
Mr Hughes' quote is still being used by Swansea council - this time in its community strategy for 2010-14 which it titles "Shared Ambition is Critical".
A Plaid Cymru spokesperson said: "In our manifesto we state that this was Dylan Thomas's mantra and it is the case these words are commonly attributed to him in a number of publications, not least by Swansea University, which is why the confusion may have arisen in the first place.
"We were advised that this association was correct, and if that is not the case then clearly we will correct our online manifesto and seek advice from elsewhere in future in terms of confirming our literary references.
"However we maintain that these words should be the guiding principle of the next Welsh Government in order to create a better Wales."