diff --git a/networks.rkt b/networks.rkt
index 93fa991..179dcd8 100644
--- a/networks.rkt
+++ b/networks.rkt
@@ -336,13 +336,13 @@
 ;;; function form for x.
 (define (list-syntactic-interactions nf x)
   (set-intersect
-   (extract-symbols (hash-ref nf x))
+   (extract-symbols (hash-ref (network-form-forms nf) x))
    (hash-keys nf)))
 
 (module+ test
   (test-case "list-syntactic-interactions"
-    (define n #hash((a . (+ a b c))
-                    (b . (- b c))))
+    (define n (make-boolean-network-form #hash((a . (+ a b c))
+                                               (b . (- b c)))))
     (check-true (set=? (list-syntactic-interactions n 'a) '(a b)))
     (check-true (set=? (list-syntactic-interactions n 'b) '(b)))))
 
@@ -366,8 +366,8 @@
 
 (module+ test
   (test-case "build-syntactic-interaction-graph"
-    (define n #hash((a . (+ a b c))
-             (b . (- b c))))
+    (define n (make-boolean-network-form #hash((a . (+ a b c))
+                                               (b . (- b c)))))
     (define ig (build-syntactic-interaction-graph n))
     (check-true (has-vertex? ig 'a))
     (check-true (has-vertex? ig 'b))