Pickups falling out of casings

[faminepulse]

I have a j-bass that I'm replacing the pickups on. Everything is cool except the actual pickup itself keeps falling out of the casing. What is the best method for keeping these two together.

[Rebop]

Installing them keeps them together.

[faminepulse]

I've installed them already, but they still fall down into the cavity.

[Synplicity]

you need to place some foam under the pickups