diff --git a/src/reactor.rs b/src/reactor.rs
index c5cd338..11004fc 100644
--- a/src/reactor.rs
+++ b/src/reactor.rs
@@ -293,6 +293,19 @@ impl ReactorLock<'_> {
                             if ev.writable {
                                 ready.append(&mut wakers.writers);
                             }
+
+                            // Re-register if there are still writers or
+                            // readers. The can happen if e.g. we were
+                            // previously interested in both readability and
+                            // writability, but only one of them was emitted.
+                            if !(wakers.writers.is_empty() && wakers.readers.is_empty()) {
+                                self.reactor.sys.reregister(
+                                    source.raw,
+                                    source.key,
+                                    !wakers.readers.is_empty(),
+                                    !wakers.writers.is_empty(),
+                                )?;
+                            }
                         }
                     }
 
diff --git a/tests/async_io.rs b/tests/async_io.rs
index 68c4826..95c3631 100644
--- a/tests/async_io.rs
+++ b/tests/async_io.rs
@@ -2,7 +2,9 @@
 use std::os::unix::net::{UnixDatagram, UnixListener, UnixStream};
 use std::{
     io,
-    net::{TcpListener, TcpStream, UdpSocket},
+    net::{Shutdown, TcpListener, TcpStream, UdpSocket},
+    sync::Arc,
+    time::Duration,
 };
 
 use futures::{AsyncReadExt, AsyncWriteExt, StreamExt};
@@ -180,3 +182,58 @@ fn uds_send_to_recv_from() -> io::Result<()> {
         Ok(())
     })
 }
+
+// Test that we correctly re-register interests when we are previously
+// interested in both readable and writable events and then we get only one of
+// them. (we need to re-register interest on the other.)
+#[test]
+fn tcp_duplex() -> io::Result<()> {
+    smol::run(async {
+        let listener = Async::<TcpListener>::bind("127.0.0.1:0")?;
+        let stream0 =
+            Arc::new(Async::<TcpStream>::connect(listener.get_ref().local_addr()?).await?);
+        let stream1 = Arc::new(listener.accept().await?.0);
+
+        async fn do_read(s: Arc<Async<TcpStream>>) -> io::Result<()> {
+            let mut buf = vec![0u8; 4096];
+            loop {
+                let len = (&*s).read(&mut buf).await?;
+                if len == 0 {
+                    return Ok(());
+                }
+            }
+        }
+
+        async fn do_write(s: Arc<Async<TcpStream>>) -> io::Result<()> {
+            let buf = vec![0u8; 4096];
+            for _ in 0..4096 {
+                (&*s).write_all(&buf).await?;
+            }
+            s.get_ref().shutdown(Shutdown::Write)?;
+            Ok(())
+        }
+
+        // Read from and write to stream0.
+        let r0 = Task::spawn(do_read(stream0.clone()));
+        let w0 = Task::spawn(do_write(stream0));
+
+        // Sleep a bit, so that reading and writing are both blocked.
+        smol::Timer::after(Duration::from_millis(5)).await;
+
+        // Start reading stream1, make stream0 writable.
+        let r1 = Task::spawn(do_read(stream1.clone()));
+
+        // Finish writing to stream0.
+        w0.await?;
+        r1.await?;
+
+        // Start writing to stream1, make stream0 readable.
+        let w1 = Task::spawn(do_write(stream1));
+
+        // Will r0 be correctly woken?
+        r0.await?;
+        w1.await?;
+
+        Ok(())
+    })
+}