"We've always said we want to make Ashton Gate a fortress and that is what has happened," Johnson told the Bristol Evening Post.
"I know we've drawn a few at home, but to go 18 unbeaten is a record we should all be proud of. It is certainly something that Wednesday will be aware of.
"They've been very complimentary about our record at Ashton Gate and have admitted this might not be the best time for them to play us here.
"Psychologically, it has to give us an advantage. Wednesday will know of our record here and they will be thinking about it in the build-up to the game."