diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 4d1f762dd26..eaea2b33204 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,8 @@
+2011-09-28  Stefan Monnier  <monnier@iro.umontreal.ca>
+
+	* emacs-lisp/debug.el (debug-convert-byte-code): Don't assume the
+	object has more than 4 slots (bug#9613).
+
 2011-09-28  Juanma Barranquero  <lekktu@gmail.com>
 
 	* subr.el (with-output-to-temp-buffer):
diff --git a/lisp/emacs-lisp/debug.el b/lisp/emacs-lisp/debug.el
index d7021a46165..d05a518e590 100644
--- a/lisp/emacs-lisp/debug.el
+++ b/lisp/emacs-lisp/debug.el
@@ -869,8 +869,10 @@ To specify a nil argument interactively, exit with an empty minibuffer."
                  ,defn
                  ,@(remq '&rest (remq '&optional args))))))
 	(if (> (length defn) 5)
+            ;; The mere presence of field 5 is sufficient to make
+            ;; it interactive.
 	    (push `(interactive ,(aref defn 5)) body))
-	(if (aref defn 4)
+	(if (and (> (length defn) 4) (aref defn 4))
 	    ;; Use `documentation' here, to get the actual string,
 	    ;; in case the compiled function has a reference
 	    ;; to the .elc file.