1 files changed, 1 insertions, 1 deletions
diff --git a/library/std/src/io/copy.rs b/library/std/src/io/copy.rs
index 1d9d93f5b64..420fc400705 100644
--- a/library/std/src/io/copy.rs
+++ b/library/std/src/io/copy.rs
@@ -86,7 +86,7 @@ impl<W: Write + ?Sized> BufferedCopySpec for W {
     }
 }
 
-impl<I: Write> BufferedCopySpec for BufWriter<I> {
+impl<I: ?Sized + Write> BufferedCopySpec for BufWriter<I> {
     fn copy_to<R: Read + ?Sized>(reader: &mut R, writer: &mut Self) -> Result<u64> {
         if writer.capacity() < DEFAULT_BUF_SIZE {
             return stack_buffer_copy(reader, writer);