Documenter With Nested Modules

I have a package, which looks something like

module MyPackage
    module Sub1
        module SubSub1
            # some code
        # some code

    module Sub2


When I try to run doctests I keep running into the following two errors

┌ Warning: Failed to evaluate `CurrentModule = SubSub1` in `@meta` block.
│   err = UndefVarError: SubSub1 not defined
└ @ Documenter.DocTests ~/.julia/packages/Documenter/XIxke/src/DocTests.jl:101

which I get in the docs file corresponding to SubSub1 where I have

CurrentModule = SubSub1
DocTestSetup  = quote
    using MyPackage
    using .MyPackage.Sub1.SubSub1

(I don’t know how to escape the backticks)

and in the doctests I get

ERROR: UndefVarError: thing in SubSub1 not defined
  [1] top-level scope
  @ none:1

Can somebody tell me how to get Documenter to load the modules deeper inside my package so they are available to use in the @meta block for CurrentModule = SubSub1 and how to load them so they are available in the doctests themselves? I’ve tried many combinations and none seem to work.