Jailed Rwandan gospel singer, Kizito Mihigo's, request for a separate appeal hearing was on Monday denied by the Supreme Court.
The judges ruled that Mr Mihigo must appear alongside his accomplice.
The 37-year-old was in February 2015 sentenced to a reduced sentence of 10 years after admitting to a plot to kill President Paul Kagame.
He was convicted alongside radio journalist Cassien Ntamuhanga, who was handed 25 years, and retired soldier Jean Paul Dukuzumuremyi, who got 30 years.
The three appealed their sentences.
However, Mr Ntamuhanga is now a fugitive after escaping from prison in October last year.
Mr Mihigo’s lawyer, Antoinette Mukasoni, on Monday argued that the prosecution’s desire to have the three appear in court would delay his quest for justice.
“The crimes that connect the three individuals are very minimal. On top of that, we cannot wait for Ntamuhanga to be rearrested for the
appeal to begin. Dukuzumuremyi refused to get a lawyer and uses it an excuse for the appeal trial to start,” Mr Mukasoni told court.
“Unlike those two, my client has expressed willingness and has done everything necessary to have the appeal trial. That is why I request
that he be tried separately in the interest of justice.”
After deliberation that lasted about 30 minutes, the judges declined the request on grounds that the crimes for which they were sentenced are connected.
The judges asked Mr Dukuzumuremyi to get a lawyer before the hearing resumes on June 11.
They however ruled that Mr Ntamuhanga’s appeal is invalid since he escaped jail, and that the trial will go on without him.
Mr Mihigo, a popular singer especially for his his renditions of the national anthem, was arrested in April 2014 and charged with terrorism.
The police accused him of being involved in activities aimed at destabilising state security and that he was working with the Rwanda National
Congress (RNC), an exiled opposition group, as well as the Democratic Forces for the Liberation of Rwanda (FDLR), a Rwandan rebel outfit in DR Congo.
In the trial that lasted six months, Mr Mihigo admitted to the charges, saying that he had been manipulated.
He was jailed for 10 years for inciting hatred and plotting to assassinate the president.
Mr Ntamuhanga and Mr Dukuzumuremyi denied the charges and claimed they had been tortured to force them to admit to the crimes.