For two years, warring parents have been unable to agree on a surname for their child.
Now they are heading back to court to argue it out.
The mother and father - known for legal reasons as Ms Reynolds and Mr Sherman - never lived together, but their "fleeting" relationship produced a baby boy in 2013.
Although the parents have agreed to share parenting of the toddler, Ms Reynolds has always insisted he take her surname while Mr Sherman wants the boy to have a double-barrelled last name.
To date, the boy has not had his name formally registered.
Among issues raised in a hearing before a Federal Circuit Court judge last year was a concern that the child would have trouble fitting a hyphenated surname on the top of homework sheets or on lunchboxes.
Another was that he might face difficulties naming his own children if he ended up marrying someone who also had a hyphenated surname.
Ms Reynolds feared the father might "disengage" from the child, leaving him with a surname that would serve "as the reminder of a man who deserted him".
But the trial judge sided with the father, saying in October: "The child has two parents and I consider it is in his best interests to have a hyphenated surname.
"As a matter of his welfare, a hyphenated surname would benefit the child possessing an identity with both families."
She instructed the parents "to use the surname (Sherman-Reynolds) at all times, both in writing and orally when referring to the child's surname".
That decision was appealed and the full bench of the Family Court of Australia has now upheld the appeal.
Justices Michelle May, Murray Aldridge and Stephen Thackray wrote in a June 30 judgment that they had "no alternative" but to send the case back to the Federal Circuit Court for re-hearing.
"We are aware of the pressures of work in a busy trial court, and are therefore sympathetic to the effort her Honour made to resolve the matter expeditiously," they added.
"Nevertheless, we consider that a dispute about the name by which a child will be known perhaps for his entire life is a matter of real importance."
