diff --git a/ipc-queue/src/fifo.rs b/ipc-queue/src/fifo.rs
index d9ca36ba..d834673a 100644
--- a/ipc-queue/src/fifo.rs
+++ b/ipc-queue/src/fifo.rs
@@ -68,7 +68,7 @@ where
     let arc = Arc::new(FifoBuffer::new(len));
     let inner = Fifo::from_arc(arc);
     let tx = AsyncSender { inner: inner.clone(), synchronizer: s.clone() };
-    let rx = AsyncReceiver { inner, synchronizer: s, read_epoch: Arc::new(AtomicU32::new(0)) };
+    let rx = AsyncReceiver { inner, synchronizer: s, read_epoch: Arc::new(AtomicU64::new(0)) };
     (tx, rx)
 }
 
diff --git a/ipc-queue/src/lib.rs b/ipc-queue/src/lib.rs
index 4cc31117..42fd7915 100644
--- a/ipc-queue/src/lib.rs
+++ b/ipc-queue/src/lib.rs
@@ -10,7 +10,7 @@
 
 use std::future::Future;
 use std::pin::Pin;
-use std::sync::atomic::AtomicU32;
+use std::sync::atomic::AtomicU64;
 use std::sync::Arc;
 
 use fortanix_sgx_abi::FifoDescriptor;
@@ -154,7 +154,7 @@ pub struct AsyncSender<T: 'static, S> {
 pub struct AsyncReceiver<T: 'static, S> {
     inner: Fifo<T>,
     synchronizer: S,
-    read_epoch: Arc<AtomicU32>,
+    read_epoch: Arc<AtomicU64>,
 }
 
 /// `DescriptorGuard<T>` can produce a `FifoDescriptor<T>` that is guaranteed
@@ -177,7 +177,7 @@ impl<T> DescriptorGuard<T> {
 /// read to/from the queue. This is useful in case we want to know whether or
 /// not a particular value written to the queue has been read.
 pub struct PositionMonitor<T: 'static> {
-    read_epoch: Arc<AtomicU32>,
+    read_epoch: Arc<AtomicU64>,
     fifo: Fifo<T>,
 }