Chinese student Xiaozheng Lin, 25, was originally jailed for 14 years for the manslaughter of Yuqi Luo, 31, and Hyun Sook Jeon, 51.
But the Victorian Court of Appeal on Wednesday re-sentenced him to 18 years behind bars after finding the original term was "manifestly inadequate".
Ms Luo and Ms Jeon were both sex workers who operated out of their apartments in Melbourne.
Lin had sex with Ms Luo at her La Trobe Street apartment in the early hours of December 27, 2022, before asking for more services.
When she told him it would cost another $100, Lin became enraged and pushed Ms Luo onto the bed, before strangling her until she was gasping for air.
He left her for dead, stealing $7000 in cash along with other personal belongings including her mobile phone, tablet and handbags.
Lin told his friend he had sex with Ms Luo, robbed and assaulted her after she had bitten his hand, and claimed she was alive when he left.
Later on December 27, between 10.15pm and 10.45pm, Lin visited Ms Jeon at her Docklands apartment where they had sex before he inflicted another deadly assault.
Lin left about 12.37am, stealing her bank cards, laptop, phone, car and building keys, and caught an Uber home.
It is unclear how Ms Jeon died because her body was too decomposed to determine a cause of death at the time of autopsy.
Lin was facing a murder trial but cut a deal with prosecutors, instead pleading guilty to two counts of manslaughter in October 2024.
He was sentenced the following month to a maximum 14 years' behind bars with a non-parole period of nine years.
Prosecutors appealed the sentence in June 2025, arguing it was manifestly inadequate given the seriousness of the offending and Lin's high moral culpability.
And appeal justices Lesley Taylor, Peter Kidd and Jane Dixon on Wednesday agreed, finding the offending called for a stern punishment.
"The objective gravity and moral culpability in respect of each offence was high and the stark feature of this case was the loss of life by, not just one, but two defenceless women," the written reasons stated.
"In our view, each of the individual sentences was outside the range reasonably open to the sentencing judge in all the circumstances."
The justices also found the non-parole period was manifestly too low given Lin was not found to have good prospects of rehabilitation. They increased it to 14 years.
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