diff --git a/src/components/net/image_cache_task.rs b/src/components/net/image_cache_task.rs
index 41ac94ca6d7..7b6970e09df 100644
--- a/src/components/net/image_cache_task.rs
+++ b/src/components/net/image_cache_task.rs
@@ -528,7 +528,7 @@ mod tests {
     use std::comm::{Empty, Data, Disconnected};
 
     trait Closure {
-        fn invoke(&self, response: Sender<resource_task::ProgressMsg>) { }
+        fn invoke(&self, _response: Sender<resource_task::ProgressMsg>) { }
     }
     struct DoesNothing;
     impl Closure for DoesNothing { }