diff --git a/Cargo.toml b/Cargo.toml
index 4e68160..257ef30 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,6 +12,7 @@ ring = "^0.12"
 protobuf = "1.4.4"
 crossbeam = "0.3.2"
 crossbeam-channel = "0.1"
+itertools = "0.7"
 
 [build-dependencies]
 protoc-rust = "1.4.4"
diff --git a/src/agreement.rs b/src/agreement.rs
index 9a02934..0cf9d94 100644
--- a/src/agreement.rs
+++ b/src/agreement.rs
@@ -1,5 +1,6 @@
 //! Binary Byzantine agreement protocol from a common coin protocol.
 
+use itertools::Itertools;
 use std::collections::{BTreeMap, BTreeSet, HashMap, VecDeque};
 use std::hash::Hash;
 
@@ -210,17 +211,12 @@ impl<NodeUid: Clone + Eq + Hash> Agreement<NodeUid> {
     /// can, however, expect every good node to send an AUX value that will
     /// eventually end up in our bin_values.
     fn count_aux(&self) -> (usize, BTreeSet<bool>) {
-        let mut count = 0;
-        let vals: BTreeSet<bool> = self.received_aux
+        let (vals_cnt, vals) = self.received_aux
             .values()
-            .filter(|b| {
-                count += 1;
-                self.bin_values.contains(b)
-            })
-            .cloned()
-            .collect();
+            .filter(|b| self.bin_values.contains(b))
+            .tee();
 
-        (count, vals)
+        (vals_cnt.count(), vals.cloned().collect())
     }
 
     /// Waits until at least (N − f) AUX_r messages have been received, such that
diff --git a/src/lib.rs b/src/lib.rs
index 58deb95..53e63f6 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -8,6 +8,7 @@
 extern crate log;
 extern crate crossbeam;
 extern crate crossbeam_channel;
+extern crate itertools;
 extern crate merkle;
 extern crate protobuf;
 extern crate reed_solomon_erasure;