diff --git a/artiq/firmware/runtime/lib.rs b/artiq/firmware/runtime/lib.rs
index 95c83a976..9949f210c 100644
--- a/artiq/firmware/runtime/lib.rs
+++ b/artiq/firmware/runtime/lib.rs
@@ -26,15 +26,6 @@ use smoltcp::wire::{EthernetAddress, IpAddress, IpCidr};
 use proto::{mgmt_proto, analyzer_proto, moninj_proto, rpc_proto, session_proto, kernel_proto};
 use amp::{mailbox, rpc_queue};
 
-macro_rules! borrow_mut {
-    ($x:expr) => ({
-        match $x.try_borrow_mut() {
-            Ok(x) => x,
-            Err(_) => panic!("cannot borrow mutably at {}:{}", file!(), line!())
-        }
-    })
-}
-
 mod config;
 mod ethmac;
 mod rtio_mgt;
@@ -157,7 +148,7 @@ fn startup() {
         scheduler.run();
 
         {
-            let sockets = &mut *borrow_mut!(scheduler.sockets());
+            let sockets = &mut *scheduler.sockets().borrow_mut();
             loop {
                 match interface.poll(sockets, board::clock::get_ms()) {
                     Ok(true) => (),
diff --git a/artiq/firmware/runtime/sched.rs b/artiq/firmware/runtime/sched.rs
index 1a6ce55b4..82738e9c4 100644
--- a/artiq/firmware/runtime/sched.rs
+++ b/artiq/firmware/runtime/sched.rs
@@ -124,7 +124,7 @@ impl Scheduler {
     pub fn run(&mut self) {
         self.sockets.borrow_mut().prune();
 
-        self.threads.append(&mut *borrow_mut!(self.spawned));
+        self.threads.append(&mut *self.spawned.borrow_mut());
         if self.threads.len() == 0 { return }
 
         let now = board::clock::get_ms();
@@ -133,7 +133,7 @@ impl Scheduler {
             self.run_idx = (self.run_idx + 1) % self.threads.len();
 
             let result = {
-                let mut thread = borrow_mut!(self.threads[self.run_idx].0);
+                let mut thread = self.threads[self.run_idx].0.borrow_mut();
                 match thread.waiting_for {
                     _ if thread.interrupted => {
                         thread.interrupted = false;
@@ -164,7 +164,7 @@ impl Scheduler {
                 },
                 Some(wait_request) => {
                     // The thread has suspended itself.
-                    let mut thread = borrow_mut!(self.threads[self.run_idx].0);
+                    let mut thread = self.threads[self.run_idx].0.borrow_mut();
                     thread.waiting_for = wait_request
                 }
             }
@@ -189,7 +189,7 @@ impl<'a> Io<'a> {
     pub fn spawn<F>(&self, stack_size: usize, f: F) -> ThreadHandle
             where F: 'static + FnOnce(Io) + Send {
         let handle = unsafe { Thread::new(self, stack_size, f) };
-        borrow_mut!(self.spawned).push(handle.clone());
+        self.spawned.borrow_mut().push(handle.clone());
         handle
     }
 
@@ -241,7 +241,7 @@ macro_rules! until {
     ($socket:expr, $ty:ty, |$var:ident| $cond:expr) => ({
         let (sockets, handle) = ($socket.io.sockets.clone(), $socket.handle);
         $socket.io.until(move || {
-            let mut sockets = borrow_mut!(sockets);
+            let mut sockets = sockets.borrow_mut();
             let $var = sockets.get::<$ty>(handle);
             $cond
         })
@@ -269,7 +269,8 @@ impl<'a> TcpListener<'a> {
     fn new_lower(io: &'a Io<'a>, buffer_size: usize) -> SocketHandle {
         let rx_buffer = vec![0; buffer_size];
         let tx_buffer = vec![0; buffer_size];
-        borrow_mut!(io.sockets)
+        io.sockets
+            .borrow_mut()
             .add(TcpSocketLower::new(
                 TcpSocketBuffer::new(rx_buffer),
                 TcpSocketBuffer::new(tx_buffer)))
@@ -286,7 +287,7 @@ impl<'a> TcpListener<'a> {
 
     fn with_lower<F, R>(&self, f: F) -> R
             where F: FnOnce(SocketRef<TcpSocketLower>) -> R {
-        let mut sockets = borrow_mut!(self.io.sockets);
+        let mut sockets = self.io.sockets.borrow_mut();
         let result = f(sockets.get(self.handle.get()));
         result
     }
@@ -327,7 +328,7 @@ impl<'a> TcpListener<'a> {
         // that still counts as accepting even though nothing may be sent.
         let (sockets, handle) = (self.io.sockets.clone(), self.handle.get());
         self.io.until(move || {
-            let mut sockets = borrow_mut!(sockets);
+            let mut sockets = sockets.borrow_mut();
             let socket = sockets.get::<TcpSocketLower>(handle);
             socket.may_send() || socket.may_recv()
         })?;
@@ -352,7 +353,7 @@ impl<'a> TcpListener<'a> {
 impl<'a> Drop for TcpListener<'a> {
     fn drop(&mut self) {
         self.with_lower(|mut s| s.close());
-        borrow_mut!(self.io.sockets).release(self.handle.get())
+        self.io.sockets.borrow_mut().release(self.handle.get())
     }
 }
 
@@ -377,7 +378,7 @@ impl<'a> TcpStream<'a> {
 
     fn with_lower<F, R>(&self, f: F) -> R
             where F: FnOnce(SocketRef<TcpSocketLower>) -> R {
-        let mut sockets = borrow_mut!(self.io.sockets);
+        let mut sockets = self.io.sockets.borrow_mut();
         let result = f(sockets.get(self.handle));
         result
     }
@@ -496,6 +497,6 @@ impl<'a> Write for TcpStream<'a> {
 impl<'a> Drop for TcpStream<'a> {
     fn drop(&mut self) {
         self.with_lower(|mut s| s.close());
-        borrow_mut!(self.io.sockets).release(self.handle)
+        self.io.sockets.borrow_mut().release(self.handle)
     }
 }
diff --git a/artiq/firmware/runtime/session.rs b/artiq/firmware/runtime/session.rs
index fa698b198..ed31860b0 100644
--- a/artiq/firmware/runtime/session.rs
+++ b/artiq/firmware/runtime/session.rs
@@ -615,7 +615,7 @@ pub fn thread(io: Io) {
     {
         let congress = congress.clone();
         respawn(&io, &mut kernel_thread, move |io| {
-            let mut congress = borrow_mut!(congress);
+            let mut congress = congress.borrow_mut();
             info!("running startup kernel");
             match flash_kernel_worker(&io, &mut congress, "startup_kernel") {
                 Ok(()) => info!("startup kernel finished"),
@@ -650,7 +650,7 @@ pub fn thread(io: Io) {
             let congress = congress.clone();
             let stream = stream.into_handle();
             respawn(&io, &mut kernel_thread, move |io| {
-                let mut congress = borrow_mut!(congress);
+                let mut congress = congress.borrow_mut();
                 let mut stream = TcpStream::from_handle(&io, stream);
                 match host_kernel_worker(&io, &mut stream, &mut *congress) {
                     Ok(()) => (),
@@ -673,7 +673,7 @@ pub fn thread(io: Io) {
 
             let congress = congress.clone();
             respawn(&io, &mut kernel_thread, move |io| {
-                let mut congress = borrow_mut!(congress);
+                let mut congress = congress.borrow_mut();
                 match flash_kernel_worker(&io, &mut *congress, "idle_kernel") {
                     Ok(()) =>
                         info!("idle kernel finished, standing by"),