diff --git a/artiq/runtime.rs/libksupport/lib.rs b/artiq/runtime.rs/libksupport/lib.rs
index 08673e759..7c0db38c1 100644
--- a/artiq/runtime.rs/libksupport/lib.rs
+++ b/artiq/runtime.rs/libksupport/lib.rs
@@ -118,6 +118,22 @@ extern fn panic_fmt(args: core::fmt::Arguments, file: &'static str, line: u32) -
     loop {}
 }
 
+#[repr(C)]
+pub struct ArtiqList<T> {
+    len: usize,
+    ptr: *const T
+}
+
+impl<T> ArtiqList<T> {
+    pub fn from_slice(slice: &'static [T]) -> ArtiqList<T> {
+        ArtiqList { ptr: slice.as_ptr(), len: slice.len() }
+    }
+
+    pub unsafe fn as_slice(&self) -> &[T] {
+        slice::from_raw_parts(self.ptr, self.len)
+    }
+}
+
 static mut NOW: u64 = 0;
 
 #[no_mangle]
@@ -221,7 +237,7 @@ extern fn watchdog_clear(id: usize) {
     send(&WatchdogClear { id: id })
 }
 
-extern fn cache_get(key: *const u8) -> (usize, *const u32) {
+extern fn cache_get(key: *const u8) -> (usize, *const i32) {
     extern { fn strlen(s: *const c_char) -> size_t; }
     let key = unsafe { slice::from_raw_parts(key, strlen(key as *const c_char)) };
     let key = unsafe { str::from_utf8_unchecked(key) };
@@ -230,13 +246,12 @@ extern fn cache_get(key: *const u8) -> (usize, *const u32) {
     recv!(&CacheGetReply { value } => (value.len(), value.as_ptr()))
 }
 
-extern fn cache_put(key: *const u8, &(len, ptr): &(usize, *const u32)) {
+extern fn cache_put(key: *const u8, list: ArtiqList<i32>) {
     extern { fn strlen(s: *const c_char) -> size_t; }
     let key = unsafe { slice::from_raw_parts(key, strlen(key as *const c_char)) };
     let key = unsafe { str::from_utf8_unchecked(key) };
 
-    let value = unsafe { slice::from_raw_parts(ptr, len) };
-    send(&CachePutRequest { key: key, value: value });
+    send(&CachePutRequest { key: key, value: unsafe { list.as_slice() } });
     recv!(&CachePutReply { succeeded } => {
         if !succeeded {
             artiq_raise!("CacheError", "cannot put into a busy cache row")
diff --git a/artiq/runtime.rs/libksupport/rtio.rs b/artiq/runtime.rs/libksupport/rtio.rs
index 60dadc815..2825888cc 100644
--- a/artiq/runtime.rs/libksupport/rtio.rs
+++ b/artiq/runtime.rs/libksupport/rtio.rs
@@ -1,6 +1,7 @@
 use board::csr;
 use core::ptr::{read_volatile, write_volatile};
 use core::slice;
+use ::ArtiqList;
 
 const RTIO_O_STATUS_FULL:           u32 = 1;
 const RTIO_O_STATUS_UNDERFLOW:      u32 = 2;
@@ -83,17 +84,16 @@ pub extern fn output(timestamp: i64, channel: u32, addr: u32, data: u32) {
     }
 }
 
-pub extern fn output_list(timestamp: i64, channel: u32, addr: u32,
-                          &(len, ptr): &(usize, *const u32)) {
+pub extern fn output_list(timestamp: i64, channel: u32, addr: u32, list: ArtiqList<i32>) {
     unsafe {
         csr::rtio::chan_sel_write(channel);
         csr::rtio::o_timestamp_write(timestamp as u64);
         csr::rtio::o_address_write(addr);
-        let data = slice::from_raw_parts(ptr, len);
+        let data = list.as_slice();
         for i in 0..data.len() {
             write_volatile(
                 csr::rtio::O_DATA_ADDR.offset((csr::rtio::O_DATA_SIZE - 1 - i) as isize),
-                data[i]);
+                data[i] as u32);
         }
         csr::rtio::o_we_write(1);
         let status = csr::rtio::o_status_read();
diff --git a/artiq/runtime.rs/src/cache.rs b/artiq/runtime.rs/src/cache.rs
index 4136b96f3..082dda287 100644
--- a/artiq/runtime.rs/src/cache.rs
+++ b/artiq/runtime.rs/src/cache.rs
@@ -4,7 +4,7 @@ use std::btree_map::BTreeMap;
 
 #[derive(Debug)]
 struct Entry {
-    data: Vec<u32>,
+    data: Vec<i32>,
     borrowed: bool
 }
 
@@ -18,7 +18,7 @@ impl Cache {
         Cache { entries: BTreeMap::new() }
     }
 
-    pub fn get(&mut self, key: &str) -> *const [u32] {
+    pub fn get(&mut self, key: &str) -> *const [i32] {
         match self.entries.get_mut(key) {
             None => &[],
             Some(ref mut entry) => {
@@ -28,7 +28,7 @@ impl Cache {
         }
     }
 
-    pub fn put(&mut self, key: &str, data: &[u32]) -> Result<(), ()> {
+    pub fn put(&mut self, key: &str, data: &[i32]) -> Result<(), ()> {
         match self.entries.get_mut(key) {
             None => (),
             Some(ref mut entry) => {
diff --git a/artiq/runtime.rs/src/kernel_proto.rs b/artiq/runtime.rs/src/kernel_proto.rs
index c015b76d2..89b90657f 100644
--- a/artiq/runtime.rs/src/kernel_proto.rs
+++ b/artiq/runtime.rs/src/kernel_proto.rs
@@ -51,8 +51,8 @@ pub enum Message<'a> {
     RpcRecvReply(Result<usize, Exception<'a>>),
 
     CacheGetRequest { key: &'a str },
-    CacheGetReply   { value: &'static [u32] },
-    CachePutRequest { key: &'a str, value: &'static [u32] },
+    CacheGetReply   { value: &'static [i32] },
+    CachePutRequest { key: &'a str, value: &'a [i32] },
     CachePutReply   { succeeded: bool },
 
     Log(fmt::Arguments<'a>),
diff --git a/artiq/runtime.rs/src/session.rs b/artiq/runtime.rs/src/session.rs
index 083cfa8a9..b2f58b5d1 100644
--- a/artiq/runtime.rs/src/session.rs
+++ b/artiq/runtime.rs/src/session.rs
@@ -406,7 +406,7 @@ fn process_kern_message(waiter: Waiter,
             &kern::CacheGetRequest { key } => {
                 let value = session.congress.cache.get(key);
                 kern_send(waiter, &kern::CacheGetReply {
-                    value: unsafe { mem::transmute::<*const [u32], &'static [u32]>(value) }
+                    value: unsafe { mem::transmute::<*const [i32], &'static [i32]>(value) }
                 })
             }
 
@@ -470,7 +470,7 @@ fn process_kern_message(waiter: Waiter,
 }
 
 fn process_kern_queued_rpc(stream: &mut TcpStream,
-                           session: &mut Session) -> io::Result<()> {
+                           _session: &mut Session) -> io::Result<()> {
     rpc_queue::dequeue(|slice| {
         trace!("comm<-kern (async RPC)");
         let length = NetworkEndian::read_u32(slice) as usize;