diff --git a/src/libstd/io/impls.rs b/src/libstd/io/impls.rs
index d6b41ceda439..fe1179a3b4a1 100644
--- a/src/libstd/io/impls.rs
+++ b/src/libstd/io/impls.rs
@@ -206,6 +206,14 @@ fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
         *self = b;
         Ok(())
     }
+
+    #[inline]
+    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
+        buf.extend_from_slice(*self);
+        let len = self.len();
+        *self = &self[len..];
+        Ok(len)
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]