trouble checking out 5.4 from git sources

[Dean S. Messing]

I'm trying (mutatis mutandis) to follow the instructions here:

  <wiki.scilab.org/GIT step by Step>

but am getting errors in trying to checkout the 5.4 branch.
I first cloned the repository using

   git clone git://git.scilab.org/scilab git_Scilab_5.4_pristine

which completed w/o error. Then:

   cd git_Scilab_5.4_pristine

and 

  git branch 5.4 refs/remotes/origin/5.4

  fatal: Not a valid object name: 'refs/remotes/origin/5.4'.

I know nothing technical about git, but I successfully did this
for the 5.3 branch and was able to maintain and update my 5.3 repo
all throughout development.

Dean