diff --git a/src/libstd/io/net/tcp.rs b/src/libstd/io/net/tcp.rs
index 89141155ae4ca..09b88ccaa7e2f 100644
--- a/src/libstd/io/net/tcp.rs
+++ b/src/libstd/io/net/tcp.rs
@@ -169,6 +169,7 @@ impl TcpStream {
     ///
     /// For clarification on the semantics of interrupting a read and a write,
     /// take a look at `set_read_timeout` and `set_write_timeout`.
+    #[experimental = "the timeout argument may change in type and value"]
     pub fn set_timeout(&mut self, timeout_ms: Option<u64>) {
         self.obj.set_timeout(timeout_ms)
     }
@@ -185,6 +186,7 @@ impl TcpStream {
     /// action is taken. Otherwise, the read operation will be scheduled to
     /// promptly return. If a timeout error is returned, then no data was read
     /// during the timeout period.
+    #[experimental = "the timeout argument may change in type and value"]
     pub fn set_read_timeout(&mut self, timeout_ms: Option<u64>) {
         self.obj.set_read_timeout(timeout_ms)
     }
@@ -211,6 +213,7 @@ impl TcpStream {
     /// does not know how many bytes were written as part of the timeout
     /// operation. It may be the case that bytes continue to be written in an
     /// asynchronous fashion after the call to write returns.
+    #[experimental = "the timeout argument may change in type and value"]
     pub fn set_write_timeout(&mut self, timeout_ms: Option<u64>) {
         self.obj.set_write_timeout(timeout_ms)
     }
diff --git a/src/libstd/io/net/udp.rs b/src/libstd/io/net/udp.rs
index 45da872ca1198..e66b2107bb107 100644
--- a/src/libstd/io/net/udp.rs
+++ b/src/libstd/io/net/udp.rs
@@ -147,6 +147,7 @@ impl UdpSocket {
     /// Sets the read/write timeout for this socket.
     ///
     /// For more information, see `TcpStream::set_timeout`
+    #[experimental = "the timeout argument may change in type and value"]
     pub fn set_timeout(&mut self, timeout_ms: Option<u64>) {
         self.obj.set_timeout(timeout_ms)
     }
@@ -154,6 +155,7 @@ impl UdpSocket {
     /// Sets the read timeout for this socket.
     ///
     /// For more information, see `TcpStream::set_timeout`
+    #[experimental = "the timeout argument may change in type and value"]
     pub fn set_read_timeout(&mut self, timeout_ms: Option<u64>) {
         self.obj.set_read_timeout(timeout_ms)
     }
@@ -161,6 +163,7 @@ impl UdpSocket {
     /// Sets the write timeout for this socket.
     ///
     /// For more information, see `TcpStream::set_timeout`
+    #[experimental = "the timeout argument may change in type and value"]
     pub fn set_write_timeout(&mut self, timeout_ms: Option<u64>) {
         self.obj.set_write_timeout(timeout_ms)
     }
diff --git a/src/libstd/io/net/unix.rs b/src/libstd/io/net/unix.rs
index ac7a0f5cdce72..1e320fe1aaed4 100644
--- a/src/libstd/io/net/unix.rs
+++ b/src/libstd/io/net/unix.rs
@@ -97,6 +97,7 @@ impl UnixStream {
     /// Sets the read/write timeout for this socket.
     ///
     /// For more information, see `TcpStream::set_timeout`
+    #[experimental = "the timeout argument may change in type and value"]
     pub fn set_timeout(&mut self, timeout_ms: Option<u64>) {
         self.obj.set_timeout(timeout_ms)
     }
@@ -104,6 +105,7 @@ impl UnixStream {
     /// Sets the read timeout for this socket.
     ///
     /// For more information, see `TcpStream::set_timeout`
+    #[experimental = "the timeout argument may change in type and value"]
     pub fn set_read_timeout(&mut self, timeout_ms: Option<u64>) {
         self.obj.set_read_timeout(timeout_ms)
     }
@@ -111,6 +113,7 @@ impl UnixStream {
     /// Sets the write timeout for this socket.
     ///
     /// For more information, see `TcpStream::set_timeout`
+    #[experimental = "the timeout argument may change in type and value"]
     pub fn set_write_timeout(&mut self, timeout_ms: Option<u64>) {
         self.obj.set_write_timeout(timeout_ms)
     }