diff --git a/src/lsp/evalmacros.lsp b/src/lsp/evalmacros.lsp
index e6f84a0a9..fdb1ce434 100644
--- a/src/lsp/evalmacros.lsp
+++ b/src/lsp/evalmacros.lsp
@@ -246,7 +246,7 @@ FORM returns no value, NIL."
   (do ((vl vars (cdr vl))
        (sym (gensym))
        (forms nil)
-       (n 0 (the fixnum (1+ n))))
+       (n 0 (truly-the fixnum (1+ n))))
       ((endp vl) `(LET ((,sym (MULTIPLE-VALUE-LIST ,form))) ,@forms))
     (declare (fixnum n))
     (push `(SETQ ,(car vl) (NTH ,n ,sym)) forms)))