diff --git a/imperative/lang.rkt b/imperative/lang.rkt
index 0fa9312..1a2b045 100644
--- a/imperative/lang.rkt
+++ b/imperative/lang.rkt
@@ -62,7 +62,8 @@
                    (provide activate!* activate!)
                    (define activated? #f)
                    (define (activate!*)
-                     #,@(reverse activation-forms))
+                     #,@(reverse activation-forms)
+                     (void))
                    (define (activate!)
                      (when (not activated?)
                        (set! activated? #t)