diff --git a/graph-typed.rkt b/graph-typed.rkt
index 9942112..5efcf59 100644
--- a/graph-typed.rkt
+++ b/graph-typed.rkt
@@ -4,4 +4,7 @@
 
 (require/typed/provide graph
   [#:opaque Graph graph?]
-  [graphviz (-> Graph String)])
+  [graphviz (-> Graph
+                [#:output Output-Port]
+                [#:colors (HashTable Any Natural)]
+                String)])