diff --git a/evm/src/keccak/keccak_stark.rs b/evm/src/keccak/keccak_stark.rs
index 53dd66ab..de80bf44 100644
--- a/evm/src/keccak/keccak_stark.rs
+++ b/evm/src/keccak/keccak_stark.rs
@@ -194,6 +194,7 @@ impl<F: RichField + Extendable<D>, const D: usize> KeccakStark<F, D> {
     }
 
     pub fn generate_trace(&self, inputs: Vec<[u64; NUM_INPUTS]>) -> Vec<PolynomialValues<F>> {
+        #[allow(unused_mut)]
         let mut timing = TimingTree::new("generate trace", log::Level::Debug);
 
         // Generate the witness, except for permuted columns in the lookup argument.
diff --git a/evm/src/lib.rs b/evm/src/lib.rs
index 47335db2..1248b3e0 100644
--- a/evm/src/lib.rs
+++ b/evm/src/lib.rs
@@ -2,6 +2,7 @@
 #![allow(clippy::needless_range_loop)]
 #![allow(clippy::too_many_arguments)]
 #![allow(clippy::type_complexity)]
+#![feature(let_chains)]
 #![feature(generic_const_exprs)]
 
 pub mod all_stark;
diff --git a/evm/src/memory/memory_stark.rs b/evm/src/memory/memory_stark.rs
index 82e10869..bc38e66d 100644
--- a/evm/src/memory/memory_stark.rs
+++ b/evm/src/memory/memory_stark.rs
@@ -192,6 +192,7 @@ impl<F: RichField + Extendable<D>, const D: usize> MemoryStark<F, D> {
     }
 
     pub(crate) fn generate_trace(&self, memory_ops: Vec<MemoryOp>) -> Vec<PolynomialValues<F>> {
+        #[allow(unused_mut)]
         let mut timing = TimingTree::new("generate trace", log::Level::Debug);
 
         // Generate most of the trace in row-major form.
diff --git a/system_zero/src/system_zero.rs b/system_zero/src/system_zero.rs
index 41d39cf7..ce44c283 100644
--- a/system_zero/src/system_zero.rs
+++ b/system_zero/src/system_zero.rs
@@ -69,7 +69,8 @@ impl<F: RichField + Extendable<D>, const D: usize> SystemZero<F, D> {
     }
 
     pub fn generate_trace(&self) -> Vec<PolynomialValues<F>> {
-        let timing = TimingTree::new("generate trace", log::Level::Debug);
+        #[allow(unused_mut)]
+        let mut timing = TimingTree::new("generate trace", log::Level::Debug);
 
         // Generate the witness, except for permuted columns in the lookup argument.
         let trace_rows = timed!(