diff --git a/src/bin/kp.rs b/src/bin/kp.rs
index 9e03e20..471d8a8 100644
--- a/src/bin/kp.rs
+++ b/src/bin/kp.rs
@@ -185,7 +185,7 @@ fn transform(
     // to compute the roundtrip differences
     let mut buffer = Vec::new();
     if options.roundtrip {
-        buffer = operands.clone();
+        buffer.clone_from(&operands);
     }
 
     let mut n = if options.inverse {