diff --git a/src/libcore/rt/io/file.rs b/src/libcore/rt/io/file.rs
index 4e3e01a5eceb..e4fe066a173f 100644
--- a/src/libcore/rt/io/file.rs
+++ b/src/libcore/rt/io/file.rs
@@ -42,7 +42,7 @@ impl FileStream {
     pub fn open<P: PathLike>(_path: &P,
                              _mode: FileMode,
                              _access: FileAccess
-                            ) -> Result<FileStream, IoError> {
+                            ) -> Option<FileStream> {
         fail!()
     }
 }
diff --git a/src/libcore/rt/io/net/tcp.rs b/src/libcore/rt/io/net/tcp.rs
index d78241b8e446..d726bae821c8 100644
--- a/src/libcore/rt/io/net/tcp.rs
+++ b/src/libcore/rt/io/net/tcp.rs
@@ -16,7 +16,7 @@ use super::ip::IpAddr;
 pub struct TcpStream;
 
 impl TcpStream {
-    pub fn connect(_addr: IpAddr) -> Result<TcpStream, IoError> {
+    pub fn connect(_addr: IpAddr) -> Option<TcpStream> {
         fail!()
     }
 }
@@ -40,7 +40,7 @@ impl Close for TcpStream {
 pub struct TcpListener;
 
 impl TcpListener {
-    pub fn bind(_addr: IpAddr) -> Result<TcpListener, IoError> {
+    pub fn bind(_addr: IpAddr) -> Option<TcpListener> {
         fail!()
     }
 }
diff --git a/src/libcore/rt/io/net/udp.rs b/src/libcore/rt/io/net/udp.rs
index 81a6677c14af..8691a697e888 100644
--- a/src/libcore/rt/io/net/udp.rs
+++ b/src/libcore/rt/io/net/udp.rs
@@ -16,7 +16,7 @@ use super::ip::IpAddr;
 pub struct UdpStream;
 
 impl UdpStream {
-    pub fn connect(_addr: IpAddr) -> Result<UdpStream, IoError> {
+    pub fn connect(_addr: IpAddr) -> Option<UdpStream> {
         fail!()
     }
 }
@@ -40,7 +40,7 @@ impl Close for UdpStream {
 pub struct UdpListener;
 
 impl UdpListener {
-    pub fn bind(_addr: IpAddr) -> Result<UdpListener, IoError> {
+    pub fn bind(_addr: IpAddr) -> Option<UdpListener> {
         fail!()
     }
 }
diff --git a/src/libcore/rt/io/net/unix.rs b/src/libcore/rt/io/net/unix.rs
index a5f4f8e3ba8b..bb3db6ec0d50 100644
--- a/src/libcore/rt/io/net/unix.rs
+++ b/src/libcore/rt/io/net/unix.rs
@@ -16,7 +16,7 @@ use super::super::support::PathLike;
 pub struct UnixStream;
 
 impl UnixStream {
-    pub fn connect<P: PathLike>(_path: &P) -> Result<UnixStream, IoError> {
+    pub fn connect<P: PathLike>(_path: &P) -> Option<UnixStream> {
         fail!()
     }
 }
@@ -40,7 +40,7 @@ impl Close for UnixStream {
 pub struct UnixListener;
 
 impl UnixListener {
-    pub fn bind<P: PathLike>(_path: &P) -> Result<UnixListener, IoError> {
+    pub fn bind<P: PathLike>(_path: &P) -> Option<UnixListener> {
         fail!()
     }
 }