diff --git a/src/libnative/io/file_unix.rs b/src/libnative/io/file_unix.rs
index 67aad1904b9..88f5061bbef 100644
--- a/src/libnative/io/file_unix.rs
+++ b/src/libnative/io/file_unix.rs
@@ -523,7 +523,7 @@ mod tests {
                 assert_eq!(buf[2], 's' as u8);
                 assert_eq!(buf[3], 't' as u8);
             }
-            r => fail!("invalid read: {:?}", r)
+            r => fail!("invalid read: {}", r)
         }
 
         assert!(writer.inner_read(buf).is_err());
@@ -547,7 +547,7 @@ mod tests {
                     assert_eq!(buf[2], 's' as u8);
                     assert_eq!(buf[3], 't' as u8);
                 }
-                r => fail!("invalid read: {:?}", r)
+                r => fail!("invalid read: {}", r)
             }
         }
     }
diff --git a/src/librustrt/rtio.rs b/src/librustrt/rtio.rs
index 1afd88edbc2..a08bc697602 100644
--- a/src/librustrt/rtio.rs
+++ b/src/librustrt/rtio.rs
@@ -356,6 +356,7 @@ pub trait PausableIdleCallback {
 
 pub trait RtioSignal {}
 
+#[deriving(Show)]
 pub struct IoError {
     pub code: uint,
     pub extra: uint,