diff --git a/src/libcore/pipes.rs b/src/libcore/pipes.rs
index 6c7be8a2ae5..c7cd098394c 100644
--- a/src/libcore/pipes.rs
+++ b/src/libcore/pipes.rs
@@ -201,10 +201,10 @@ impl PacketHeader {
 }
 
 #[doc(hidden)]
-pub type Packet<T: Owned> = {
+pub struct Packet<T: Owned> {
     header: PacketHeader,
     mut payload: Option<T>,
-};
+}
 
 #[doc(hidden)]
 pub trait HasBuffer {
@@ -223,9 +223,9 @@ impl<T: Owned> Packet<T>: HasBuffer {
 
 #[doc(hidden)]
 pub fn mk_packet<T: Owned>() -> Packet<T> {
-    {
+    Packet {
         header: PacketHeader(),
-        mut payload: None
+        payload: None,
     }
 }
 
@@ -233,9 +233,9 @@ pub fn mk_packet<T: Owned>() -> Packet<T> {
 fn unibuffer<T: Owned>() -> ~Buffer<Packet<T>> {
     let b = ~{
         header: BufferHeader(),
-        data: {
+        data: Packet {
             header: PacketHeader(),
-            mut payload: None,
+            payload: None,
         }
     };
 
@@ -1011,7 +1011,9 @@ pub trait Peekable<T> {
 }
 
 #[doc(hidden)]
-type Chan_<T:Owned> = { mut endp: Option<streamp::client::Open<T>> };
+struct Chan_<T:Owned> {
+    mut endp: Option<streamp::client::Open<T>>,
+}
 
 /// An endpoint that can send many messages.
 pub enum Chan<T:Owned> {
@@ -1019,7 +1021,9 @@ pub enum Chan<T:Owned> {
 }
 
 #[doc(hidden)]
-type Port_<T:Owned> = { mut endp: Option<streamp::server::Open<T>> };
+struct Port_<T:Owned> {
+    mut endp: Option<streamp::server::Open<T>>,
+}
 
 /// An endpoint that can receive many messages.
 pub enum Port<T:Owned> {
@@ -1034,7 +1038,7 @@ These allow sending or receiving an unlimited number of messages.
 pub fn stream<T:Owned>() -> (Port<T>, Chan<T>) {
     let (c, s) = streamp::init();
 
-    (Port_({ mut endp: Some(move s) }), Chan_({ mut endp: Some(move c) }))
+    (Port_(Port_ { endp: Some(s) }), Chan_(Chan_{ endp: Some(c) }))
 }
 
 impl<T: Owned> Chan<T>: GenericChan<T> {