diff --git a/src/bin/08.rs b/src/bin/08.rs
index 37191c0..14c24ad 100644
--- a/src/bin/08.rs
+++ b/src/bin/08.rs
@@ -46,8 +46,8 @@ fn part2(input: &str) -> usize {
 }
 
 fn connect(mut circuits: Vec<Circuit>, (a, b): (JBox, JBox)) -> Vec<Circuit> {
-    let with_a = circuits.iter_mut().position(|c| c.contains(&a));
-    let with_b = circuits.iter_mut().position(|c| c.contains(&b));
+    let with_a = circuits.iter().position(|c| c.contains(&a));
+    let with_b = circuits.iter().position(|c| c.contains(&b));
     match (with_a, with_b) {
         (Some(with_a), Some(with_b)) => {
             // Merge into with_a. with_b will be empty, but whatever.
@@ -71,8 +71,7 @@ fn pairs(boxes: &[JBox]) -> impl Iterator<Item = (JBox, JBox)> + use<'_> {
     boxes
         .iter()
         .copied()
-        .combinations(2)
-        .map(|v| (v[0], v[1]))
+        .tuple_combinations()
         .sorted_by_key(|&(a, b)| distance(a, b))
 }