diff --git a/artiq/firmware/ksupport/lib.rs b/artiq/firmware/ksupport/lib.rs
index 904c069e1..d7ea126ae 100644
--- a/artiq/firmware/ksupport/lib.rs
+++ b/artiq/firmware/ksupport/lib.rs
@@ -167,7 +167,7 @@ extern fn rpc_recv(slot: *mut ()) -> usize {
     })
 }
 
-fn terminate(exception: &eh::Exception, mut backtrace: &mut [usize]) -> ! {
+fn terminate(exception: &eh::Exception, backtrace: &mut [usize]) -> ! {
     let mut cursor = 0;
     for index in 0..backtrace.len() {
         if backtrace[index] > kernel_proto::KERNELCPU_PAYLOAD_ADDRESS {
@@ -333,8 +333,8 @@ extern fn dma_record_output_wide(timestamp: i64, channel: i32, address: i32, wor
         if DMA_RECORDER.buffer.len() - DMA_RECORDER.data_len < length {
             dma_record_flush()
         }
-        let mut dst = &mut DMA_RECORDER.buffer[DMA_RECORDER.data_len..
-                                               DMA_RECORDER.data_len + length];
+        let dst = &mut DMA_RECORDER.buffer[DMA_RECORDER.data_len..
+                                           DMA_RECORDER.data_len + length];
         dst[..header_length].copy_from_slice(&header[..]);
         dst[header_length..].copy_from_slice(&data[..]);
         DMA_RECORDER.data_len += length;
diff --git a/artiq/firmware/runtime/config.rs b/artiq/firmware/runtime/config.rs
index c4b45ee6c..4a1407a08 100644
--- a/artiq/firmware/runtime/config.rs
+++ b/artiq/firmware/runtime/config.rs
@@ -10,9 +10,9 @@ mod imp {
 
     mod lock {
         use core::slice;
-        use core::sync::atomic::{AtomicUsize, Ordering};
+        use core::sync::atomic::{AtomicUsize, Ordering, ATOMIC_USIZE_INIT};
 
-        static LOCKED: AtomicUsize = AtomicUsize::new(0);
+        static LOCKED: AtomicUsize = ATOMIC_USIZE_INIT;
 
         pub struct Lock;