problem with missing blueprints

[thoughtafter]

I noticed that in my dev environment for a rails 3.1.0 project when
config.cache_classes = false the blueprint disappears after the first
request.

When using XapianDb.search the 2nd request gives the error:

Blueprint for class Object is not defined

when using Object.search the 2nd request gives the error:

undefined method `search' for #<Class:0x0000000797f098>

Everything works fine with config.cache_classes = true (which of
course is the default for production env).