Problem switching branches in submodule

Hello,

I have a git repository with lots of submodules. In one particular submodule, I'm having the following problem:

If I try to switch branches at the top-level of that submodule, I succeed.

But, if I try to switch branches in any subsequen levels, I get the following error:

    fatal: internal error: work tree has already been set
    Current worktree: ../path/Mailman3/rest_project
    New worktree: ../path/Mailman3/rest_project/website/public_rest

Here, Mailman3 is the primary repository and "rest_project" is a submodule. I can do "git checkout" just fine inside rest_project, but not after cd-ing into any other repos.

My git version is 1.8.4

Other commands, like git status, push/pull are working fine.

I'd appreciate any help. Thank you.