The striker, who goes by the nickname "the Beast", donned the red strip to the Chairboys' Marlow base after Jurgen Klopp's side captured their first league title in 30 years on Thursday.
Akinfenwa opted to celebrate the Premier League triumph by attending training the next day wearing a Liverpool shirt.
And posting a video on Instagram, the ex-AFC Wimbledon man admitted he'd already agreed to pay a fine with Chairboys boss Gareth Ainsworth.
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He said: 'I'm happily going to take the fine. I've already paid my gaffer, he knows.
'There's a lot of hate I'm getting today, a lot of hate! But it's cool, I'll take it!'
Pompey could face Wycombe in the play-off final on Monday, July 13.
The Blues face Oxford United, while the Chairboys take on Fleetwood Town next week.
The victors of both respective two-legged clashes will then face off at Wembley for promotion to the Championship.