upper/lowercase in Lisp functions



Hello,
is this a bug or intended?

Foo.lisp:

(defun $Foo (x) x)


(%i10) load("F:\\home\\maxima\\Foo.lisp");
(%o10) 			    F:\home\maxima\Foo.lisp
(%i11) Foo(3);
(%o11) 				    Foo(3)
(%i12) foo(3);
(%o12) 				       3

Volker