diff --git a/README.md b/README.md
index dc409d72..d47f72a3 100644
--- a/README.md
+++ b/README.md
@@ -64,7 +64,7 @@ just run webserver
 
 To run Fix-on-Arca, run:
 ```sh
-just fix addblob.fix
+just fix eval addblob.fix
 ```
 
 # License
diff --git a/common/src/buddy.rs b/common/src/buddy.rs
index cec5b170..fd31d6c0 100644
--- a/common/src/buddy.rs
+++ b/common/src/buddy.rs
@@ -622,7 +622,7 @@ impl BuddyAllocatorImpl {
     pub fn set_caching(&self, enable: bool) -> bool {
         if cfg!(feature = "cache") {
             self.caching
-                .fetch_update(Ordering::SeqCst, Ordering::SeqCst, |_| Some(enable))
+                .try_update(Ordering::SeqCst, Ordering::SeqCst, |_| Some(enable))
                 .unwrap_or_else(|x| x)
         } else {
             false
diff --git a/common/src/pipe/uni.rs b/common/src/pipe/uni.rs
index 7282f082..02f9867e 100644
--- a/common/src/pipe/uni.rs
+++ b/common/src/pipe/uni.rs
@@ -133,17 +133,20 @@ pub struct Reader {
 impl Reader {
     pub fn read(&mut self, data: &mut [u8]) -> Result<usize> {
         unsafe {
+            // Drain any buffered bytes before reporting the writer's hangup, so a
+            // reader still sees data the writer sent immediately before closing
+            // (e.g. a Close-ack the peer wrote just before dropping its end).
+            if self.ring.as_ref().unwrap().can_read() {
+                let bytes = self.ring.as_ref().unwrap().readable_bytes();
+                let len = core::cmp::min(data.len(), bytes.len());
+                data[..len].copy_from_slice(&(&(*bytes))[..len]);
+                self.ring.as_mut().unwrap().read(len);
+                return Ok(len);
+            }
             if self.is_closed() {
                 return Err(Error::Closed);
             }
-            if !self.ring.as_ref().unwrap().can_read() {
-                return Err(Error::WouldBlock);
-            }
-            let bytes = self.ring.as_ref().unwrap().readable_bytes();
-            let len = core::cmp::min(data.len(), bytes.len());
-            data[..len].copy_from_slice(&(&(*bytes))[..len]);
-            self.ring.as_mut().unwrap().read(len);
-            Ok(len)
+            Err(Error::WouldBlock)
         }
     }
 
diff --git a/common/src/util/concurrent_trie.rs b/common/src/util/concurrent_trie.rs
index afb8c67d..b4ee0969 100644
--- a/common/src/util/concurrent_trie.rs
+++ b/common/src/util/concurrent_trie.rs
@@ -38,7 +38,7 @@ impl<T> SyncBox<T> {
         unsafe {
             Some(Box::from_raw(
                 self.ptr
-                    .fetch_update(Ordering::SeqCst, Ordering::SeqCst, |old| {
+                    .try_update(Ordering::SeqCst, Ordering::SeqCst, |old| {
                         if old.is_null() {
                             None
                         } else {
@@ -54,7 +54,7 @@ impl<T> SyncBox<T> {
         let ptr = Box::into_raw(value);
         unsafe {
             self.ptr
-                .fetch_update(Ordering::SeqCst, Ordering::SeqCst, |old| {
+                .try_update(Ordering::SeqCst, Ordering::SeqCst, |old| {
                     if old.is_null() {
                         Some(ptr)
                     } else {
diff --git a/vmm/src/comm.rs b/vmm/src/comm.rs
index 860d1b1e..61172a54 100644
--- a/vmm/src/comm.rs
+++ b/vmm/src/comm.rs
@@ -99,6 +99,7 @@ pub fn file_thread(mut file: File, mut pipe: FilePipe) {
                 Response::Offset(offset)
             }
             Request::Close => {
+                pipe.send(&Response::Ack);
                 return;
             }
         };
@@ -120,6 +121,7 @@ pub fn listener_thread(listener: TcpListener, mut pipe: ListenerPipe) {
                 Response::Pipe(decompose_pipe(p))
             }
             Request::Close => {
+                pipe.send(&Response::Ack);
                 return;
             }
         };
@@ -142,6 +144,7 @@ pub fn stream_thread(mut stream: TcpStream, mut pipe: StreamPipe) {
                 Response::Length(len)
             }
             Request::Close => {
+                pipe.send(&Response::Ack);
                 return;
             }
         };