diff --git a/library/std/src/fs.rs b/library/std/src/fs.rs
index c550378e7d6b7..1c63280fb0ca6 100644
--- a/library/std/src/fs.rs
+++ b/library/std/src/fs.rs
@@ -795,6 +795,11 @@ impl Seek for File {
     fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
         self.inner.seek(pos)
     }
+
+    fn stream_len(&mut self) -> io::Result<u64> {
+        let file_attr = self.inner.file_attr()?;
+        Ok(file_attr.size())
+    }
 }
 #[stable(feature = "rust1", since = "1.0.0")]
 impl Read for &File {
@@ -851,6 +856,10 @@ impl Seek for &File {
     fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
         self.inner.seek(pos)
     }
+    fn stream_len(&mut self) -> io::Result<u64> {
+        let file_attr = self.inner.file_attr()?;
+        Ok(file_attr.size())
+    }
 }
 
 impl OpenOptions {
diff --git a/library/std/src/io/buffered/bufreader.rs b/library/std/src/io/buffered/bufreader.rs
index 4f339a18a480e..0b64d4ab4434b 100644
--- a/library/std/src/io/buffered/bufreader.rs
+++ b/library/std/src/io/buffered/bufreader.rs
@@ -489,6 +489,10 @@ impl<R: Seek> Seek for BufReader<R> {
             )
         })
     }
+
+    fn stream_len(&mut self) -> io::Result<u64> {
+        self.inner.stream_len()
+    }
 }
 
 impl<T> SizeHint for BufReader<T> {
diff --git a/library/std/src/io/buffered/bufwriter.rs b/library/std/src/io/buffered/bufwriter.rs
index 6acb937e78479..d7697db878c9b 100644
--- a/library/std/src/io/buffered/bufwriter.rs
+++ b/library/std/src/io/buffered/bufwriter.rs
@@ -661,6 +661,10 @@ impl<W: Write + Seek> Seek for BufWriter<W> {
         self.flush_buf()?;
         self.get_mut().seek(pos)
     }
+
+    fn stream_len(&mut self) -> io::Result<u64> {
+        self.inner.stream_len()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/library/std/src/io/impls.rs b/library/std/src/io/impls.rs
index e5048dcc8acd9..bcbf978432b3b 100644
--- a/library/std/src/io/impls.rs
+++ b/library/std/src/io/impls.rs
@@ -93,6 +93,11 @@ impl<S: Seek + ?Sized> Seek for &mut S {
     fn stream_position(&mut self) -> io::Result<u64> {
         (**self).stream_position()
     }
+
+    #[inline]
+    fn stream_len(&mut self) -> io::Result<u64> {
+        (**self).stream_len()
+    }
 }
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<B: BufRead + ?Sized> BufRead for &mut B {
@@ -197,6 +202,11 @@ impl<S: Seek + ?Sized> Seek for Box<S> {
     fn stream_position(&mut self) -> io::Result<u64> {
         (**self).stream_position()
     }
+
+    #[inline]
+    fn stream_len(&mut self) -> io::Result<u64> {
+        (**self).stream_len()
+    }
 }
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<B: BufRead + ?Sized> BufRead for Box<B> {