fatal: Not a valid object name: ‘master’

I have a private server running git 1.7
When I

git init 

a folder it doesn’t create a master branch.
Cause when i do:

git branch 

it doesn’t list anything.
When I do:

git --bare init

it creates the files.
When I type

git branch master 

it says:

fatal: Not a valid object name: 'master'.