A French court on Wednesday banned a couple from giving their baby a name containing a tilde, ruling that the "n with a squiggle over it" was incompatible with national law.
The couple from Brittany wanted to call their newborn baby boy Fañch, a traditional name in the northwestern region which has its own language.
"The principle according to which babies' names are chosen by their mothers and fathers must have limits when it comes to using a spelling which includes a character unrecognised by the French language," the court in the town of Quimper said in its judgment.
Fañch is a name borne notably by two Breton writers, Fañch Peru and Fañch Broudig.
The tilde, an "n" with a small sideways "s" written over it, is commonly used in Spanish.
An official in Quimper had initially refused to write "Fañch" on the baby's birth certificate, before changing their mind a few days later.
Born in May, the baby already has an ID card and passport with the tilda on it.
His furious father Jean-Christophe Bernard said the battle wasn't over.
"He will have his tilde, that's for sure," Bernard said.
"When? We don't know. We'll see with a lawyer and with the town hall what we can do."