The former Germany international striker, now the team's general manager, accidentally revealed at a press conference that the game is set to be held next year, despite the fixture not being formally announced by FIFA or either nation's governing body.
It will be Australia's first meeting with 'Die Mannschaft' since they came from behind to upset Joachim Loew's side 2-1 in Moenchengladbach in March 2011, having lost 4-0 to Germany at the 2010 FIFA World Cup.
The Socceroos, who will host the Asian Cup in January, take on Japan next Tuesday, while Germany are in Euro 2016 qualifying action against Gibraltar this weekend, before a friendly against Spain.