diff --git a/src/libstd/flatpipes.rs b/src/libstd/flatpipes.rs
index 88de53f3605..b091a951af1 100644
--- a/src/libstd/flatpipes.rs
+++ b/src/libstd/flatpipes.rs
@@ -558,9 +558,11 @@ pub mod bytepipes {
         }
     }
 
+    // XXX: Remove `@mut` when this module is ported to the new I/O traits,
+    // which use `&mut self` properly.
     pub struct PipeBytePort {
         port: comm::Port<~[u8]>,
-        mut buf: ~[u8]
+        buf: @mut ~[u8]
     }
 
     pub struct PipeByteChan {
@@ -569,13 +571,13 @@ pub mod bytepipes {
 
     impl BytePort for PipeBytePort {
         fn try_recv(&self, count: uint) -> Option<~[u8]> {
-            if vec::uniq_len(&const self.buf) >= count {
-                let mut bytes = ::core::util::replace(&mut self.buf, ~[]);
-                self.buf = bytes.slice(count, bytes.len()).to_owned();
+            if vec::uniq_len(&const *self.buf) >= count {
+                let mut bytes = ::core::util::replace(&mut *self.buf, ~[]);
+                *self.buf = bytes.slice(count, bytes.len()).to_owned();
                 bytes.truncate(count);
                 return Some(bytes);
-            } else if vec::uniq_len(&const self.buf) > 0 {
-                let mut bytes = ::core::util::replace(&mut self.buf, ~[]);
+            } else if vec::uniq_len(&const *self.buf) > 0 {
+                let mut bytes = ::core::util::replace(&mut *self.buf, ~[]);
                 assert!(count > bytes.len());
                 match self.try_recv(count - bytes.len()) {
                     Some(rest) => {
@@ -584,11 +586,11 @@ pub mod bytepipes {
                     }
                     None => return None
                 }
-            } else if vec::uniq_len(&const self.buf) == 0 {
+            } else if vec::uniq_len(&const *self.buf) == 0 {
                 match self.port.try_recv() {
                     Some(buf) => {
                         assert!(!buf.is_empty());
-                        self.buf = buf;
+                        *self.buf = buf;
                         return self.try_recv(count);
                     }
                     None => return None
@@ -609,7 +611,7 @@ pub mod bytepipes {
         fn new(p: Port<~[u8]>) -> PipeBytePort {
             PipeBytePort {
                 port: p,
-                buf: ~[]
+                buf: @mut ~[]
             }
         }
     }
diff --git a/src/libstd/io_util.rs b/src/libstd/io_util.rs
index 50d2eb6a785..6ed626202b7 100644
--- a/src/libstd/io_util.rs
+++ b/src/libstd/io_util.rs
@@ -13,14 +13,14 @@ use core::io;
 
 pub struct BufReader {
     buf: ~[u8],
-    mut pos: uint
+    pos: @mut uint
 }
 
 pub impl BufReader {
     pub fn new(v: ~[u8]) -> BufReader {
         BufReader {
             buf: v,
-            pos: 0
+            pos: @mut 0
         }
     }
 
@@ -29,13 +29,13 @@ pub impl BufReader {
         // I can't get the borrowing to work correctly
         let bytes_reader = BytesReader {
             bytes: ::core::util::id::<&[u8]>(self.buf),
-            pos: self.pos
+            pos: *self.pos
         };
 
         let res = f(&bytes_reader);
 
         // FIXME #4429: This isn't correct if f fails
-        self.pos = bytes_reader.pos;
+        *self.pos = bytes_reader.pos;
 
         return res;
     }