diff --git a/command-parser/benches/commands.rs b/command-parser/benches/commands.rs
index c61d526355c..c2791e3c17f 100644
--- a/command-parser/benches/commands.rs
+++ b/command-parser/benches/commands.rs
@@ -3,6 +3,7 @@ use patricia_tree::PatriciaSet;
 use std::{
     borrow::Cow,
     collections::{BTreeSet, HashSet},
+    iter::FromIterator,
 };
 
 fn btreeset(set: &BTreeSet<Cow<'static, str>>, needle: &str) {
@@ -77,7 +78,7 @@ fn criterion_benchmark(c: &mut Criterion) {
     ];
 
     c.bench_function("c: btreeset", |b| {
-        let mut set = BTreeSet::from_iter(commands.iter().map(Cow::from));
+        let set = BTreeSet::from_iter(commands.iter().map(|e| Cow::from(*e)));
 
         b.iter(|| {
             for command in commands.iter() {
@@ -87,7 +88,7 @@ fn criterion_benchmark(c: &mut Criterion) {
     });
 
     c.bench_function("c: hashset", |b| {
-        let mut set = HashSet::from_iter(commands.iter().map(Cow::from));
+        let set = HashSet::from_iter(commands.iter().map(|e| Cow::from(*e)));
 
         for e in commands.iter() {
             set.insert(Cow::from(*e));