Doctor Who writers had to change the script for the show's Easter special after a double-decker bus being used for filming got damaged.
The episode Planet of the Dead sees David Tennant and guest star Michelle Ryan going on a dangerous bus trip.
One bus is being used for shooting scenes in Cardiff, and the top deck of a second bus was damaged as it arrived in Dubai.
A spokeswoman for the show said filming was "continuing as normal".
But parts of the script, written by Russell T Davies and co-writer Gareth Roberts, had to be changed because of the damage.
Planet of the Dead is the first of four Doctor Who specials, which will bring an end to David Tennant's time as the Doctor.