Evaluating this:

(let ((x (make-array '(1) :element-type '(signed-byte 32))))
  (setf (aref x 0) 1))

gives this error:

size mismatch: #<SB-VM::EA :DWORD base=#<SB-C:TN t1[RDX]> disp=1> is a :DWORD and #<SB-C:TN t2[RAX]> is a :QWORD.

It works if I use 16 or 8 instead of 32 in '(signed-byte 32).
I'm on a AMD64 running fedora core 5 with the RPM package of sbcl (version 0.9.12).

Marco