diff --git a/mls-rs/src/tree_kem/parent_hash.rs b/mls-rs/src/tree_kem/parent_hash.rs
index f04157a7..15ff5dd5 100644
--- a/mls-rs/src/tree_kem/parent_hash.rs
+++ b/mls-rs/src/tree_kem/parent_hash.rs
@@ -135,7 +135,7 @@ impl TreeKemPublic {
             )
             .await?;
 
-            (parent.parent_hash, hash) = (hash, calculated);
+            (parent.parent_hash = std::mem::replace(&mut hash, calculated);
         }
 
         Ok(hash)