diff --git a/module/language/cps/intset.scm b/module/language/cps/intset.scm
index 382a4ba6d..87956c525 100644
--- a/module/language/cps/intset.scm
+++ b/module/language/cps/intset.scm
@@ -34,6 +34,7 @@
             transient-intset?
             persistent-intset
             transient-intset
+            intset
             intset-add
             intset-add!
             intset-remove
@@ -300,6 +301,11 @@
        ;; Add a new level and try again.
        (intset-add (add-level min shift root) i))))))
 
+(define-syntax intset
+  (syntax-rules ()
+    ((intset) empty-intset)
+    ((intset x x* ...) (intset-add (intset x* ...) x))))
+
 (define (intset-remove bs i)
   (define (remove i shift root)
     (cond
diff --git a/module/language/cps2/simplify.scm b/module/language/cps2/simplify.scm
index a9355cd00..5aa1bb129 100644
--- a/module/language/cps2/simplify.scm
+++ b/module/language/cps2/simplify.scm
@@ -56,9 +56,10 @@
   (persistent-intmap
    (intmap-fold (lambda (k v out)
                   (let ((v* (f k v)))
-                    (if (equal? v v*)
-                        out
-                        (intmap-replace! out k v*))))
+                    (cond
+                     ((equal? v v*) out)
+                     (v* (intmap-replace! out k v*))
+                     (else (intmap-remove out k)))))
                 conts
                 conts)))