diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index b5bfd2dce80b..666e69c20595 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -29,6 +29,7 @@ use fold::Folder;
 use std::collections::HashMap;
 use std::rc::Rc;
 
+#[deprecated="Replaced by MultiItemDecorator"]
 pub trait ItemDecorator {
     fn expand(&self,
               ecx: &mut ExtCtxt,