AFL UMPIRES coach Hayden Kennedy says he was surprised by field umpire Jordan Bannister's use of Twitter to concede he made a crucial mistake during Saturday's Hawthorn and Melbourne clash.

Bannister paid an incorrect free kick to Hawk Kade Stewart after the debutant ducked into a James Harmes tackle during the fourth quarter of the game, with the scores level.

The decision created widespread discussion on social media, but the experienced umpire nipped the issue in the bud by acknowledging via his Twitter account that it was a "s*** free".

Kennedy told AFL.com.au's Whistleblowers program he didn't have a problem with Bannister's admission of guilt, but didn't want the practice to become commonplace for umpires.

"When I found out about (the tweet) it was a little bit surprising," he said.

"It was great he was able to do that (and) stop the conversations that were going on.

"We do make a fair few mistakes each week, so we don't want the (umpires) every time we make a mistake to tweet out that 'I apologise'.

"We don't want to make a habit of that, but I'm happy with it."

Kennedy said his charges received social media training and were well aware of the AFL's policies.