diff --git a/src/cmp/cmpprop.lsp b/src/cmp/cmpprop.lsp
index 17bf4ea44..a676e2ae4 100644
--- a/src/cmp/cmpprop.lsp
+++ b/src/cmp/cmpprop.lsp
@@ -339,7 +339,7 @@ compute it. This version only handles the simplest cases."
                  'character)
                 ((eq array 'base-string)
                  'base-char)
-                ((member (setf array (expand-deftype array))
+                ((member (setf array (si::expand-deftype array))
                          '(array vector simple-array))
                  t)
                 ((atom array)
diff --git a/src/cmp/cmptype.lsp b/src/cmp/cmptype.lsp
index 13f553846..6faa196a1 100644
--- a/src/cmp/cmptype.lsp
+++ b/src/cmp/cmptype.lsp
@@ -42,16 +42,6 @@
         (c1constant-value new-value :only-small-values t)
         (c1nil))))
 
-(defun expand-deftype (type)
-  (let (base args)
-    (if (atom type)
-        (setf base type args nil)
-        (setf base (car type) args (cdr type)))
-    (let ((fn (get-sysprop base 'SI::DEFTYPE-DEFINITION)))
-      (if fn
-          (expand-deftype (apply fn args))
-          type))))
-
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;
 ;; TYPE CHECKING