Former Stoke City academy player Andrew Hall will have to serve an extra five years in prison for murdering his girlfriend.
The 18-year-old was handed a 10-year sentence for the death of 15-year-old Megan-Leigh Peat, who was attacked by Hall with kitchen and vegetable knives, in September.
Despite the first ruling, three judges and the Attorney General Dominic Grieve QC agreed at the Court of Appeal that the teenager should be handed a longer sentence.
Lady Justice Rafferty said: "The extreme brutality of the attack, involving many blows with the knife, some of sufficient force to cause blood spatter and deep penetrating wounds to the skull, were an aggravating factor."
Luton Crown Court heard in September that Hall had "just lost it" during the attack.
