diff --git a/benches/workloads.rs b/benches/workloads.rs
index faae7da..77c0598 100644
--- a/benches/workloads.rs
+++ b/benches/workloads.rs
@@ -46,8 +46,6 @@ const CAPACITY: usize = 4096;
 const UNIVERSE: u64 = 16_384;
 const OPS: usize = 200_000;
 const SEED: u64 = 42;
-/// Read-through probability used by the operation model (1.0 = always read-through).
-const READ_THROUGH_RATIO: f64 = 1.0;
 
 fn make_generator(workload: Workload) -> WorkloadGenerator {
     WorkloadSpec {
@@ -99,7 +97,13 @@ fn bench_hit_rates(c: &mut Criterion) {
                                     &mut generator,
                                     OPS,
                                     &mut op_model,
-                                    |k| Arc::clone(&value_pool[k as usize]),
+                                    |k| {
+                                        Arc::clone(
+                                            value_pool
+                                                .get(k as usize)
+                                                .expect("generator produced key outside configured UNIVERSE"),
+                                        )
+                                    },
                                 );
                                 total += start.elapsed();
                             }
@@ -214,7 +218,16 @@ fn bench_comprehensive(c: &mut Criterion) {
                                     policy_id,
                                     &mut cache,
                                     cfg,
-                                    |key| Arc::clone(&value_pool[key as usize]),
+                                    |key| {
+                                        let idx = key as usize;
+                                        Arc::clone(value_pool.get(idx).unwrap_or_else(|| {
+                                            panic!(
+                                                "workload key {} out of range for value_pool (len {}, expected < UNIVERSE)",
+                                                key,
+                                                value_pool.len()
+                                            )
+                                        }))
+                                    },
                                 );
                                 total += start.elapsed();
                             }