golang and godep : Build\install after a golang dependency update when using godep?

I have followed the instructions @ https://github.com/tools/godep regarding updating a dependency but when I go to build\install using the altered version it has not been updated within Godeps/_workspace/pkg

So I have

go get github.com/golang/glog
godep save
godep go install

and I can see

1. The modification timestamp in Godeps/_workspace/pkg/linux_amd64/github.com/golang/glog.a
2. The rev commit value in Godeps/Godeps.json

but now when I want to update I follow the instructions

go get github.com/golang/glog
godep update github.com/golang/glog
godep go install

I observe the following

1. The Godeps/Godeps.json rev commit has been updated
2. Godeps/_workspace/src/github.com/golang/ source is updated
3. But the file timestamp for odeps/_workspace/pkg/linux_amd64/github.com/golang/glog.a is not updated hence we are using the previous version

I believe I should add a .gitignore entry for pkg and bin, which means we would do a clean build on a fresh git clone

I know I could do a rm -r on both the pkg and bin directories before the godep go install command

Is this expected behavior ?

Thanks in advance
Pat

FYI

Since golang v1.4 I can now use the -a flag for the go install command, since it now longer tries to rebuild the standard library, see the v1.4 release notes section on the change to the build -a flag

Obviously this does not apply in pre v1.4 as it will attempt to rebuild the standard library packages