1 files changed, 7 insertions, 1 deletions
diff --git a/src/libsyntax/ptr.rs b/src/libsyntax/ptr.rs
index b86d19ba3ce..bb47d9b535b 100644
--- a/src/libsyntax/ptr.rs
+++ b/src/libsyntax/ptr.rs
@@ -38,7 +38,7 @@
 
 use std::fmt::{self, Display, Debug};
 use std::iter::FromIterator;
-use std::ops::Deref;
+use std::ops::{Deref, DerefMut};
 use std::{mem, ptr, slice, vec};
 
 use serialize::{Encodable, Decodable, Encoder, Decoder};
@@ -103,6 +103,12 @@ impl<T: ?Sized> Deref for P<T> {
     }
 }
 
+impl<T: ?Sized> DerefMut for P<T> {
+    fn deref_mut(&mut self) -> &mut T {
+        &mut self.ptr
+    }
+}
+
 impl<T: 'static + Clone> Clone for P<T> {
     fn clone(&self) -> P<T> {
         P((**self).clone())