diff --git a/src/reactor.rs b/src/reactor.rs
index edd5166..26e4a62 100644
--- a/src/reactor.rs
+++ b/src/reactor.rs
@@ -25,7 +25,7 @@ use std::mem;
 use std::os::unix::io::RawFd;
 #[cfg(windows)]
 use std::os::windows::io::{FromRawSocket, RawSocket};
-use std::sync::atomic::{AtomicU64, AtomicUsize, Ordering};
+use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::Arc;
 use std::task::{Poll, Waker};
 use std::time::{Duration, Instant};
@@ -53,7 +53,7 @@ pub(crate) struct Reactor {
     sys: sys::Reactor,
 
     /// Ticker bumped before polling.
-    ticker: AtomicU64,
+    ticker: AtomicUsize,
 
     /// Registered sources.
     sources: piper::Mutex<Slab<Arc<Source>>>,
@@ -86,7 +86,7 @@ impl Reactor {
     pub fn get() -> &'static Reactor {
         static REACTOR: Lazy<Reactor> = Lazy::new(|| Reactor {
             sys: sys::Reactor::new().expect("cannot initialize I/O event notification"),
-            ticker: AtomicU64::new(0),
+            ticker: AtomicUsize::new(0),
             sources: piper::Mutex::new(Slab::new()),
             events: piper::Mutex::new(sys::Events::new()),
             timers: piper::Mutex::new(BTreeMap::new()),
@@ -359,10 +359,10 @@ pub(crate) struct Source {
 #[derive(Debug)]
 struct Wakers {
     /// Last reactor tick that delivered a readability event.
-    tick_readable: u64,
+    tick_readable: usize,
 
     /// Last reactor tick that delivered a writability event.
-    tick_writable: u64,
+    tick_writable: usize,
 
     /// Tasks waiting for the next readability event.
     readers: Vec<Waker>,
@@ -383,14 +383,16 @@ impl Source {
 
     /// Waits until the I/O source is readable.
     pub(crate) async fn readable(&self) -> io::Result<()> {
-        let mut tick = None;
+        let mut ticks = None;
 
         future::poll_fn(|cx| {
             let mut wakers = self.wakers.lock();
 
             // Check if the reactor has delivered a readability event.
-            if let Some(tick) = tick {
-                if wakers.tick_readable > tick {
+            if let Some((a, b)) = ticks {
+                // If `tick_readable` has changed to a value other than the old reactor tick, that
+                // means a newer reactor tick has delivered a readability event.
+                if wakers.tick_readable != a && wakers.tick_readable != b {
                     return Poll::Ready(Ok(()));
                 }
             }
@@ -410,9 +412,12 @@ impl Source {
                 wakers.readers.push(cx.waker().clone());
             }
 
-            // Remember the current reactor tick.
-            if tick.is_none() {
-                tick = Some(Reactor::get().ticker.load(Ordering::SeqCst));
+            // Remember the current ticks.
+            if ticks.is_none() {
+                ticks = Some((
+                    Reactor::get().ticker.load(Ordering::SeqCst),
+                    wakers.tick_readable,
+                ));
             }
 
             Poll::Pending
@@ -422,14 +427,16 @@ impl Source {
 
     /// Waits until the I/O source is writable.
     pub(crate) async fn writable(&self) -> io::Result<()> {
-        let mut tick = None;
+        let mut ticks = None;
 
         future::poll_fn(|cx| {
             let mut wakers = self.wakers.lock();
 
             // Check if the reactor has delivered a writability event.
-            if let Some(tick) = tick {
-                if wakers.tick_writable > tick {
+            if let Some((a, b)) = ticks {
+                // If `tick_writable` has changed to a value other than the old reactor tick, that
+                // means a newer reactor tick has delivered a writability event.
+                if wakers.tick_writable != a && wakers.tick_writable != b {
                     return Poll::Ready(Ok(()));
                 }
             }
@@ -449,9 +456,12 @@ impl Source {
                 wakers.writers.push(cx.waker().clone());
             }
 
-            // Remember the current reactor tick.
-            if tick.is_none() {
-                tick = Some(Reactor::get().ticker.load(Ordering::SeqCst));
+            // Remember the current ticks.
+            if ticks.is_none() {
+                ticks = Some((
+                    Reactor::get().ticker.load(Ordering::SeqCst),
+                    wakers.tick_writable,
+                ));
             }
 
             Poll::Pending