vendor/vendor after new dependency

I have v0.13.2 and i just experienced a very strange bug. I added new dependency with glide get, as usual, but i ended up with two vendor directories:

/vendor/vendor/github.com/... /vendor/google.golang.org/

which broke everything. Once I deleted the entire vendor and installed with glide i, all is good. This never happened so I have no idea wtf was that but it is maybe worth reporting.