The competition is heating up as the celebrities battled it out for a chance to perform at Blackpool.
But as they geared up for another dramatic show, viewers realised there was something amiss.
After Susan Calman and Kevin Clifton had performed the Tango to Firework by Katy Perry, host Tess Daly announced the singers.
As she rushed through the line-up, fans of the BBC dancing competition were quick to realise that regular vocalist Hayley was missing.
BBCStrictly Come Dancing: Tess Daly revealed a change in the singing line-up
BBCStrictly Come Dancing: New singer Tori had replaced regular vocalist Hayley
Instead, the singer had been replaced by Tori and viewers were given no explanation regarding Hayley's absence.
Fans rushed to Twitter to comment on the change, with one noting: "Erm, WHERE IS HAYLEY THE SINGER?! #scd #Strictly (sic)."
While another added: "The singer who's replacing Hayley tonight is doing really well #Strictly."
"NEW FEMALE SINGER! What happened to Hayley? #scd #strictly," a third continued.
BBCStrictly Come Dancing: There were some changes to the music line-up
Someone else shared: "New female singer alert! #SCD #Strictly."
As a fifth asked: "New singer on #Strictly?"
Strictly Come Dancing continues on Sunday on BBC One at 7.20pm.