diff --git a/src/cmp/cmpopt-type.lsp b/src/cmp/cmpopt-type.lsp
index 0dd9e86bd..c3b0711e7 100644
--- a/src/cmp/cmpopt-type.lsp
+++ b/src/cmp/cmpopt-type.lsp
@@ -23,12 +23,14 @@
            (declare (:read-only ,%limit))
            (ext:compiler-typecase ,%limit
              (fixnum
+	      ;; %LIMIT will be type checked by the compiler to be
+	      ;; a fixnum. We may thus just increase the counter.
 	      (let ((,variable 0))
 		(declare (fixnum ,variable)
 			 ,@declarations)
 		(si::while (< ,variable ,%limit)
                   ,@body
-		  (setq ,variable (the fixnum (1+ ,variable))))))
+		  (reckless (setq ,variable (1+ ,variable))))))
              (t
 	      (let ((,variable 0))
 		(declare ,@declarations)