diff --git a/src/libsyntax/ext/deriving/clone.rs b/src/libsyntax/ext/deriving/clone.rs
index fccc67bf220..f6b8c00e761 100644
--- a/src/libsyntax/ext/deriving/clone.rs
+++ b/src/libsyntax/ext/deriving/clone.rs
@@ -60,7 +60,7 @@ fn cs_clone(
         cx.ident_of("Clone"),
         cx.ident_of("clone"),
     ];
-    let subcall = |field: &FieldInfo| {
+    let subcall = |&: field: &FieldInfo| {
         let args = vec![cx.expr_addr_of(field.span, field.self_.clone())];
 
         cx.expr_call_global(field.span, fn_path.clone(), args)
diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index ea305642f66..5d5b56d444f 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -25,6 +25,7 @@
 #![allow(unknown_features)]
 #![feature(macro_rules, globs, default_type_params, phase, slicing_syntax)]
 #![feature(quote, unsafe_destructor, import_shadowing)]
+#![feature(unboxed_closures)]
 
 extern crate arena;
 extern crate fmt_macros;
diff --git a/src/libsyntax/owned_slice.rs b/src/libsyntax/owned_slice.rs
index 43b428b5a1c..8e418e46921 100644
--- a/src/libsyntax/owned_slice.rs
+++ b/src/libsyntax/owned_slice.rs
@@ -49,7 +49,7 @@ impl<T> OwnedSlice<T> {
         self.into_vec().into_iter()
     }
 
-    pub fn map<U>(&self, f: |&T| -> U) -> OwnedSlice<U> {
+    pub fn map<U, F: FnMut(&T) -> U>(&self, f: F) -> OwnedSlice<U> {
         self.iter().map(f).collect()
     }
 }