diff --git a/day_1/benches/day_1.rs b/day_1/benches/day_1.rs
index c2855f6..e3e78c5 100644
--- a/day_1/benches/day_1.rs
+++ b/day_1/benches/day_1.rs
@@ -1,16 +1,16 @@
-use criterion::{criterion_group, criterion_main, Criterion};
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
 use day_1::day_1::{input, part_1, part_2};
 
 fn criterion_benchmark(c: &mut Criterion) {
     let input = input();
     c.bench_function("day 1 part 1", |b| {
         b.iter(|| {
-            part_1(&mut input.iter().copied());
+            black_box(part_1(&mut input.iter().copied()));
         })
     });
     c.bench_function("day 1 part 2", |b| {
         b.iter(|| {
-            part_2(&input);
+            black_box(part_2(&input));
         })
     });
 }