diff --git a/src/librustc/middle/graph.rs b/src/librustc/middle/graph.rs
index e3a89fe2525..3d5e4b167a3 100644
--- a/src/librustc/middle/graph.rs
+++ b/src/librustc/middle/graph.rs
@@ -55,7 +55,7 @@ pub struct Edge<E> {
     pub data: E,
 }
 
-#[deriving(PartialEq)]
+#[deriving(PartialEq, Show)]
 pub struct NodeIndex(pub uint);
 pub static InvalidNodeIndex: NodeIndex = NodeIndex(uint::MAX);