diff --git a/src/libstd/fs/mod.rs b/src/libstd/fs/mod.rs
index ba89b3a0ea63f..0aae59921967d 100644
--- a/src/libstd/fs/mod.rs
+++ b/src/libstd/fs/mod.rs
@@ -73,6 +73,11 @@ pub struct Metadata(fs_imp::FileAttr);
 /// will yield instances of `io::Result<DirEntry>`. Through a `DirEntry`
 /// information like the entry's path and possibly other metadata can be
 /// learned.
+///
+/// # Failure
+///
+/// This `io::Result` will be an `Err` if there's some sort of intermittent
+/// IO error during iteration.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct ReadDir(fs_imp::ReadDir);