diff --git a/networks.rkt b/networks.rkt
index 28c5d64..5765165 100644
--- a/networks.rkt
+++ b/networks.rkt
@@ -174,6 +174,10 @@
 ;;; state.
 (define update-function/c (-> state? any/c))
 
+;;; A domain mapping is a hash set mapping variables to the lists of
+;;; values in their domains.
+(define domain-mapping/c (hash/c variable? list?))
+
 ;;; A network consists of a mapping from its variables to its update
 ;;; variables, as a well as of a mapping from its variables to
 ;;; their domains.
@@ -334,10 +338,6 @@
     (check-false (has-edge? ig 'c 'b))
     (check-false (has-edge? ig 'c 'a))))
 
-;;; A domain mapping is a hash set mapping variables to the lists of
-;;; values in their domains.
-(define domain-mapping/c (hash/c variable? list?))
-
 ;;; Given a hash-set mapping variables to generic sets of their
 ;;; possible values, constructs the list of all possible states.
 (define (build-all-states vars-domains)