Setting selenium to use custom profile, but it keeps opening with default

I am trying to use python and selenium to automate some tasks in firefox. When I download a file, that pop up comes up asking if you want to open or save, and a check box for do this every time with this kind of file. I have found that check box does not work unless you install the add on Web Page Fixer. I have that installed normally, but when I use python + selenium it uses a profile with no add