diff --git a/experiments/2024-12-09/src/view.rs b/experiments/2024-12-09/src/view.rs
index 3109ff5c1..da6abd1d0 100644
--- a/experiments/2024-12-09/src/view.rs
+++ b/experiments/2024-12-09/src/view.rs
@@ -54,13 +54,13 @@ impl OperationView {
         &self,
         selected: bool,
         indent_level: usize,
-    ) -> impl Iterator<Item = (&Self, bool, usize)> {
-        iter::once((self, selected, indent_level)).chain(
+    ) -> Box<dyn Iterator<Item = (&Self, bool, usize)> + '_> {
+        Box::new(iter::once((self, selected, indent_level)).chain(
             self.children.iter().enumerate().map(move |(i, view)| {
                 let selected = Some(i) == self.selected;
                 (view, selected, indent_level + 1)
             }),
-        )
+        ))
     }
 
     fn last_index(&self) -> usize {