Mistake in LISP tutorial

I think I have found a mistake in the LISP tutorial included with GNU CLISP distributions:

Excerpt from line 711-722 of the tutorial:
-------------------------------------------------------------------------------
> (setf a (make-array 1)) ;setf on a variable is equivalent to setq
#(NIL)
> (push 5 (aref a 1)) ;push can act like setf ;???
(5)
> (pop (aref a 1)) ;so can pop
5
> (setf (aref a 1) 5)
5
> (incf (aref a 1)) ;incf reads from a place, increments,
6 ;and writes back
> (aref a 1)
6
-------------------------------------------------------------------------------

I think all the "(aref a 1)" forms above are wrong: Because we created array with one element, the only valid array index is zero; accessing index 1 (with the form "(aref a 1)") will result in an error.