diff --git a/networks.rkt b/networks.rkt
index d22bcb6..4ce3eab 100644
--- a/networks.rkt
+++ b/networks.rkt
@@ -404,14 +404,15 @@
 ;;; state f(s') in which the value for y is different from f(s).
 (define (interaction? network doms x y)
   (define states-not-x (build-all-states (hash-remove doms x)))
+  (define dom-x (hash-ref doms x))
+  (define y-func (hash-ref network y))
   (define (different-ys-exist? st)
-    (define x-states (for/list ([x-val (in-list (hash-ref doms x))])
+    (define x-states (for/list ([x-val (in-list dom-x)])
                        (hash-set st x x-val)))
     (for*/first ([st1 x-states]
                  [st2 x-states]
                  #:unless (equal? (hash-ref st1 x) (hash-ref st2 x))
-                 #:unless (equal? ((hash-ref network y) st1)
-                                  ((hash-ref network y) st2)))
+                 #:unless (equal? (y-func st1) (y-func st2)))
       #t))
   (for*/first ([st (in-list states-not-x)]
                #:when (different-ys-exist? st))