diff --git a/bitcoin/src/psbt/serialize.rs b/bitcoin/src/psbt/serialize.rs
index 4c2b0f481..703bcb79d 100644
--- a/bitcoin/src/psbt/serialize.rs
+++ b/bitcoin/src/psbt/serialize.rs
@@ -206,7 +206,7 @@ impl Serialize for KeySource {
 
         rv.append(&mut self.0.to_byte_array().to_vec());
 
-        for cnum in self.1.into_iter() {
+        for cnum in &self.1 {
             rv.append(&mut serialize(&u32::from(*cnum)))
         }