AN aspiring rapper shocked a Melbourne courtroom by pleading not guilty to raping murdered international student Aiia Maasarwe before reverting to his original guilty plea.

Codey Herrmann pleaded guilty last week to killing Ms Maasarwe whose body was found near a tram stop in Melbourne's north on January 16.

But when he was officially arraigned in the Supreme Court today he stroked his beard and answered "not guilty" to the rape charge, prompting intervention from his barrister and a do-over where he pleaded guilty to both charges.

Ms Maasarwe, 21, was walking home after a night at a comedy club when she was attacked after getting off a tram near La Trobe University in Bundoora.

A Palestinian Arab of Israeli citizenship, she had spent several months in Melbourne on a study-abroad program and was speaking by phone to her overseas-based sister when she was attacked.

Her body was not found until the following morning.

Herrmann, aged 20 at the time of his arrest, was charged three days after the crime.

The attack shocked a city still coming to grips with the recent rape and murder of Eurydice Dixon.

Ms Maasarwe's family travelled to Melbourne where a number of large vigils were held to remember the 21-year-old.

Hermann posted rap songs on his Facebook account before the murder and went by a rap alias McCodez.

On January 8, he posted this eerie message: "International girl of mystery, you knows who you are."