diff --git a/library/core/src/io/cursor.rs b/library/core/src/io/cursor.rs
index fe4def531a84a..704900f9c590e 100644
--- a/library/core/src/io/cursor.rs
+++ b/library/core/src/io/cursor.rs
@@ -486,6 +486,7 @@ pub trait WriteThroughCursor: Sized {
 }
 
 #[doc(hidden)]
+#[stable(feature = "rust1", since = "1.0.0")]
 impl<W: WriteThroughCursor> Write for Cursor<W> {
     #[inline]
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {