The Walkinshaw Andretti United driver qualified second for the 32-lap heat, however he's now been stripped of that result and will start 26th.

That's thanks to a technical breach, the front bodywork of his WAU Holden found to be wider than permitted by the regulations.

According to the team the issue stemmed from damage to the car during the session.

"After sustaining damage to the front bodywork at urn 10 during Race 25 qualifying, car #25 was ruled to have exceeded the permitted front bodywork width post session, a breach of Rule C2.1," read a WAU statement.

"While extremely disappointed with the penalty, our focus for car #25 is to now gain the best possible result from the rear of grid."

The Mostert penalty means Anton De Pasquale will be promoted to the front row of the grid alongside polesitter Shane van Gisbergen.