diff --git a/networks-tests.rkt b/networks-tests.rkt
index 05441df..c37b083 100644
--- a/networks-tests.rkt
+++ b/networks-tests.rkt
@@ -112,6 +112,7 @@
 
 (test-case "Dynamics of networks"
   (check-equal? (pretty-print-state (st '((a . #f) (b . 3) (c . 4)))) "a:#f b:3 c:4")
+  (check-equal? (pretty-print-modalities (list (set 'a) (set 'b 'a))) "{a}{a b}")
   (check-equal? (pretty-print-boolean-state (st '((a . #f) (b . #t) (c . #t)))) "a:0 b:1 c:1")
   (let ([vars '(a b c)])
     (check-equal? (make-asyn vars) (set (set 'a) (set 'b) (set 'c)))
diff --git a/networks.rkt b/networks.rkt
index 92b2b92..fc78008 100644
--- a/networks.rkt
+++ b/networks.rkt
@@ -47,6 +47,7 @@
                [dds-build-state-graph-annotated (-> dynamics? (set/c state? #:kind 'dont-care) graph?)]
                [dds-build-n-step-state-graph-annotated (-> dynamics? (set/c state? #:kind 'dont-care) number? graph?)]
                [pretty-print-state (-> state? string?)]
+               [pretty-print-modalities (-> (listof modality?) string?)]
                [any->boolean (-> any/c boolean?)]
                [pretty-print-boolean-state (-> state? string?)]
                [pretty-print-state-graph-with (-> graph? (-> state? string?) graph?)]
@@ -343,10 +344,15 @@
 (define (pretty-print-boolean-state s)
   (string-join (hash-map s (λ (key val) (format "~a:~a" key (any->boolean val))) #t)))
 
+;;; Pretty-prints a list of modalities, as suitable for showing on
+;;; state graphs.
+(define (pretty-print-modalities ms)
+  (string-join (for/list ([m ms]) (format "{~a}" (pretty-print-set m))) ""))
+
 ;;; Given a state graph and a pretty-printer for states build a new
 ;;; state graph with pretty-printed vertices and edges.
 (define (pretty-print-state-graph-with gr pprinter)
-  (update-graph gr #:v-func pprinter #:e-func pretty-print-set))
+  (update-graph gr #:v-func pprinter #:e-func pretty-print-modalities))
 
 ;;; Pretty prints a state graph with pretty-print-state.
 (define (pretty-print-state-graph gr)