diff --git a/networks.rkt b/networks.rkt
index 86f5668..3008fc4 100644
--- a/networks.rkt
+++ b/networks.rkt
@@ -510,8 +510,8 @@
          (check-equal? (graphviz (build-signed-interaction-graph/form n2))
                        "digraph G {\n\tnode0 [label=\"y\"];\n\tnode1 [label=\"t\"];\n\tnode2 [label=\"z\"];\n\tnode3 [label=\"x\"];\n\tsubgraph U {\n\t\tedge [dir=none];\n\t\tnode0 -> node0 [label=\"1\"];\n\t}\n\tsubgraph D {\n\t\tnode0 -> node1 [label=\"0\"];\n\t\tnode0 -> node2 [label=\"-1\"];\n\t\tnode0 -> node3 [label=\"1\"];\n\t}\n}\n")])))
 
-  (define-type Modality (Setof Variable))
-  (define-type Mode (Setof Modality))
+  (define-type Modality (Listof Variable))
+  (define-type Mode (Listof Modality))
   )
 
 (require 'typed)
diff --git a/scribblings/networks.scrbl b/scribblings/networks.scrbl
index c903306..d5d216c 100644
--- a/scribblings/networks.scrbl
+++ b/scribblings/networks.scrbl
@@ -365,14 +365,14 @@ values represented as 0 and 1.
 
 @deftype[Modality]{
 
-A modality is a set of variables.  This is a synonym of @racket[(Setof
+A modality is a list of variables.  This is a synonym of @racket[(Listof
 Variable)].
 
 }
 
 @deftype[Mode]{
 
-A mode is a set of modalities.  This is a synonym of @racket[(Setof Modality)].
+A mode is a list of modalities.  This is a synonym of @racket[(Listof Modality)].
 
 }