diff --git a/crates/committer/src/patricia_merkle_tree/filled_tree.rs b/crates/committer/src/patricia_merkle_tree/filled_tree.rs
index 161448dd..f733e229 100644
--- a/crates/committer/src/patricia_merkle_tree/filled_tree.rs
+++ b/crates/committer/src/patricia_merkle_tree/filled_tree.rs
@@ -7,6 +7,7 @@ use crate::patricia_merkle_tree::errors::FilledTreeError;
 use crate::patricia_merkle_tree::filled_node::FilledNode;
 use crate::patricia_merkle_tree::types::{LeafDataTrait, NodeIndex};
 use crate::storage::storage_trait::Storage;
+use crate::storage::storage_trait::StorageKey;
 
 /// Consider a Patricia-Merkle Tree which has been updated with new leaves.
 /// FilledTree consists of all nodes which were modified in the update, including their updated
@@ -14,7 +15,8 @@ use crate::storage::storage_trait::Storage;
 pub(crate) trait FilledTree<L: LeafDataTrait> {
     /// Serializes the tree into storage. Returns hash set of keys of the serialized nodes,
     /// if successful.
-    fn serialize(&self, storage: impl Storage) -> Result<HashSet<&[u8]>, FilledTreeError>;
+    fn serialize(&self, storage: &mut impl Storage)
+        -> Result<HashSet<StorageKey>, FilledTreeError>;
 }
 
 pub(crate) struct FilledTreeImpl<L: LeafDataTrait> {
diff --git a/crates/committer/src/patricia_merkle_tree/original_skeleton_tree.rs b/crates/committer/src/patricia_merkle_tree/original_skeleton_tree.rs
index 710029d2..c51a6c59 100644
--- a/crates/committer/src/patricia_merkle_tree/original_skeleton_tree.rs
+++ b/crates/committer/src/patricia_merkle_tree/original_skeleton_tree.rs
@@ -15,11 +15,11 @@ pub(crate) type OriginalSkeletonTreeResult<T> = Result<T, OriginalSkeletonTreeEr
 /// nodes on the Merkle paths from the updated leaves to the root.
 pub(crate) trait OriginalSkeletonTree<L: LeafDataTrait> {
     fn compute_original_skeleton_tree(
-        storage: impl Storage,
-        leaf_indices: &[NodeIndex],
+        storage: &impl Storage,
+        leaf_indices: [NodeIndex],
         root_hash: HashOutput,
         tree_height: TreeHeight,
-    ) -> OriginalSkeletonTreeResult<Box<Self>>;
+    ) -> OriginalSkeletonTreeResult<impl OriginalSkeletonTree<L>>;
 
     /// Computes and returns updated skeleton tree.
     fn compute_updated_skeleton_tree(