diff --git a/src/libextra/io_util.rs b/src/libextra/io_util.rs
index 91424ae3ba2..11dea1c3a70 100644
--- a/src/libextra/io_util.rs
+++ b/src/libextra/io_util.rs
@@ -10,6 +10,7 @@
 
 use core::io::{Reader, BytesReader};
 use core::io;
+use core::cast;
 
 /// An implementation of the io::Reader interface which reads a buffer of bytes
 pub struct BufReader {
@@ -29,10 +30,13 @@ impl BufReader {
     }
 
     fn as_bytes_reader<A>(&self, f: &fn(&BytesReader) -> A) -> A {
+        // XXX FIXME(#5723)
+        let bytes = ::core::util::id::<&[u8]>(self.buf);
+        let bytes: &'static [u8] = unsafe { cast::transmute(bytes) };
         // Recreating the BytesReader state every call since
         // I can't get the borrowing to work correctly
         let bytes_reader = BytesReader {
-            bytes: ::core::util::id::<&[u8]>(self.buf),
+            bytes: bytes,
             pos: @mut *self.pos
         };
 
diff --git a/src/libstd/io.rs b/src/libstd/io.rs
index 71a0dd6b9b2..a78be9c8b2b 100644
--- a/src/libstd/io.rs
+++ b/src/libstd/io.rs
@@ -1042,12 +1042,14 @@ pub fn file_reader(path: &Path) -> Result<@Reader, ~str> {
 
 
 // Byte readers
-pub struct BytesReader<'self> {
-    bytes: &'self [u8],
+pub struct BytesReader {
+    // FIXME(#5723) see other FIXME below
+    // FIXME(#7268) this should also be parameterized over <'self>
+    bytes: &'static [u8],
     pos: @mut uint
 }
 
-impl<'self> Reader for BytesReader<'self> {
+impl Reader for BytesReader {
     fn read(&self, bytes: &mut [u8], len: uint) -> uint {
         let count = uint::min(len, self.bytes.len() - *self.pos);
 
@@ -1084,6 +1086,10 @@ impl<'self> Reader for BytesReader<'self> {
 }
 
 pub fn with_bytes_reader<T>(bytes: &[u8], f: &fn(@Reader) -> T) -> T {
+    // XXX XXX XXX this is glaringly unsound
+    // FIXME(#5723) Use a &Reader for the callback's argument. Should be:
+    // fn with_bytes_reader<'r, T>(bytes: &'r [u8], f: &fn(&'r Reader) -> T) -> T
+    let bytes: &'static [u8] = unsafe { cast::transmute(bytes) };
     f(@BytesReader {
         bytes: bytes,
         pos: @mut 0
@@ -1091,6 +1097,7 @@ pub fn with_bytes_reader<T>(bytes: &[u8], f: &fn(@Reader) -> T) -> T {
 }
 
 pub fn with_str_reader<T>(s: &str, f: &fn(@Reader) -> T) -> T {
+    // FIXME(#5723): As above.
     with_bytes_reader(s.as_bytes(), f)
 }