diff --git a/networks.rkt b/networks.rkt
index 697b34c..1e79fc2 100644
--- a/networks.rkt
+++ b/networks.rkt
@@ -1280,4 +1280,11 @@
     (define n (tbn->network tbn))
     (define s1 (make-state '((a . 0) (b . 0))))
     (check-equal? (update n s1 '(a b))
+                  (make-state '((a . 0) (b . 1))))
+
+    (define sbn (make-sbn `((a . ,(make-sbf/state '((b . -1))))
+                            (b . ,(make-sbf/state '((a . 1)))))))
+    (define sn (tbn->network sbn))
+    (define s2 (make-state '((a . 1) (b . 1))))
+    (check-equal? (update sn s2 '(a b))
                   (make-state '((a . 0) (b . 1))))))