diff --git a/src/lsp/predlib.lsp b/src/lsp/predlib.lsp
index 251a17058..e54af8996 100644
--- a/src/lsp/predlib.lsp
+++ b/src/lsp/predlib.lsp
@@ -19,9 +19,8 @@
 (defvar *upgraded-array-element-type-cache* (si:make-vector t 128 nil nil nil 0))
 
 (defun subtypep-clear-cache ()
-  (when (fboundp 'fill)
-    (fill *subtypep-cache* nil)
-    (fill *upgraded-array-element-type-cache* nil)))
+  (si:fill-array-with-elt *subtypep-cache* nil 0 nil)
+  (si:fill-array-with-elt *upgraded-array-element-type-cache* nil 0 nil))
 
 (defun create-type-name (name)
   (when (member name *alien-declarations*)