Can't install PIL after Mac OS X 10.9

I've just updated my Mac OS to 10.9 and I discovered that some (all?) of my Python modules are not here anymore, especially the Image one.

So I try to execute sudo pip install pil, but I get this error:

    /Applications/ fatal error: 'X11/Xlib.h' file not found

    #      include <X11/Xlib.h>


    1 error generated.

    error: command 'cc' failed with exit status 1

My Xcode is up-to-date and I don't have any idea. Is it possible that PIL is not yet 10.9 compatible ?

Following worked for me:

    ln -s  /Applications/ /usr/local/include/X11
    sudo pip install pil


But there is more correct solution below, provided by Will.

open your terminal and execute: xcode-select --install