diff --git a/benches/hot_path.rs b/benches/hot_path.rs
index ecd84ae..accfcf2 100644
--- a/benches/hot_path.rs
+++ b/benches/hot_path.rs
@@ -3,14 +3,13 @@ use std::net::Ipv4Addr;
 
 use numa::buffer::BytePacketBuffer;
 use numa::cache::DnsCache;
-use numa::header::{DnsHeader, ResultCode};
+use numa::header::ResultCode;
 use numa::packet::DnsPacket;
 use numa::question::{DnsQuestion, QueryType};
 use numa::record::DnsRecord;
 
 fn make_response(domain: &str) -> DnsPacket {
     let mut pkt = DnsPacket::new();
-    pkt.header = DnsHeader::new();
     pkt.header.id = 0x1234;
     pkt.header.response = true;
     pkt.header.recursion_desired = true;
@@ -93,7 +92,7 @@ fn bench_cache_lookup_hit(c: &mut Criterion) {
 }
 
 fn bench_cache_lookup_miss(c: &mut Criterion) {
-    let mut cache = DnsCache::new(10_000, 60, 86400);
+    let cache = DnsCache::new(10_000, 60, 86400);
 
     c.bench_function("cache_lookup_miss", |b| {
         b.iter(|| cache.lookup(black_box("nonexistent.com"), QueryType::A))
diff --git a/benches/throughput.rs b/benches/throughput.rs
index 688b4e0..e01a25c 100644
--- a/benches/throughput.rs
+++ b/benches/throughput.rs
@@ -37,7 +37,7 @@ fn make_response(domain: &str) -> DnsPacket {
 
 /// Simulates the complete cached query pipeline (sans network I/O):
 /// parse → cache lookup → TTL adjust → serialize response
-fn simulate_cached_pipeline(query_wire: &[u8], cache: &mut numa::cache::DnsCache) -> usize {
+fn simulate_cached_pipeline(query_wire: &[u8], cache: &numa::cache::DnsCache) -> usize {
     let mut buf = BytePacketBuffer::from_bytes(query_wire);
     let query = DnsPacket::from_buffer(&mut buf).unwrap();
     let q = &query.questions[0];
@@ -71,7 +71,7 @@ fn bench_pipeline_throughput(c: &mut Criterion) {
             b.iter(|| {
                 for _ in 0..count {
                     let wire = &query_wires[idx % query_wires.len()];
-                    simulate_cached_pipeline(wire, &mut cache);
+                    simulate_cached_pipeline(wire, &cache);
                     idx += 1;
                 }
             });