Speaking last year, the 50-0 boxer told TMZ: "When I face Khabib, of course, I'm getting a nine-figure payday."
But talk of a sensational cross-sport match-up has since gone cold.
But Khabib's father, Abdulmanap, has now given his son the green light to go ahead and fight Mayweather, who has been in retirement since fighting Conor McGregor in 2017.
However, not until the 'Eagle' has fought Tony Ferguson.
"Floyd, I respect your wish to fight Khabib," he said on Instagram.
"At the moment we have our most crucial moment, when he have to hold the best fight in the history of the UFC.
"Twelve against 12 in a series of victories (in the UFC) and all the fans are waiting for this fight.
"We’ve been preparing for this fight for more than a year. Five months and the fight (with Ferguson) should take place.
"First of all we will need to do some boxing training and we need a camp – with Lomachenko Sr for half a year. Why not!!!"
Over the summer, Khabib's manager Ali Abdelaziz claimed Mayweather - who is nicknamed 'Money' - needed the fight due to being short of cash.
"Floyd Mayweather to this day keeps begging to fight Khabib, begging!" he told TMZ.
“Floyd’s running out of money.
“I'm telling you, people reaching out to me every week about Floyd to fight Khabib but at the end of the day, we're not interested, for now.”
It's unlikely that Mayweather will be short of cash, however.
The unbeaten boxer is worth between $700m (£544m) and $1bn (£780m) following his stellar and high-profile career
And Mayweather reportedly earned $9m (£7m) for his farcical bout with Tenshin Nasukawa on New Year's Eve.
Conor McGregor fought the American in 2017, losing to a TKO in the 10th round.
The Irishman is making his return to the Octagon in January and has called out Khabib for a rematch of their own.
However, the Dagestan fighter is not interested in another fight with McGregor.