[TYPO3-core] Error in fresh git clone installation

[Frank Frewer]

Hello,

I just made a fresh install from a new git clone.
PHP Version 5.5.19

No problems with the install procedure, but when I try to get into the 
backend I have got this error:

PHP Fatal error:  Class 
'TYPO3\\CMS\\Backend\\Toolbar\\ShortcutToolbarItem' not found in 
/var/customers/typo3_src/typo3_src-git/typo3/sysext/core/Classes/Utility/GeneralUtility.php 
on line 4384

What did I wrong?

Thanks
Frank