diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index b63678881f6..d3cedee6d21 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -431,6 +431,7 @@ pub enum SyntaxExtension {
 
     /// A syntax extension that is attached to an item and modifies it
     /// in-place.
+    #[deprecated="Replaced by MultiModifier"]
     Modifier(Box<ItemModifier + 'static>),
 
     /// A syntax extension that is attached to an item and modifies it