diff --git a/handouts/src/28.3-unblocking.md b/handouts/src/28.3-unblocking.md
index d9ddf38810065f44ddf5f5d63708b693d9f01425..d16c69dbe654806a03eab9c00fdb5bdfad210f1c 100644
--- a/handouts/src/28.3-unblocking.md
+++ b/handouts/src/28.3-unblocking.md
@@ -72,6 +72,9 @@ std::thread::scope(|s| {
       // Need to hint the compiler about the output error type
       Ok::<_, Box<dyn Error>>(())
 })?;
+
+// Remove final hdf5.close(), this will now be handled by the I/O thread
+Ok(())
 ```
 
 Then we set up FIFO communication channels with the I/O threads, making sure