diff --git a/tests/phase0/helpers.py b/tests/phase0/helpers.py
index 8c8064fc1..e20bb9484 100644
--- a/tests/phase0/helpers.py
+++ b/tests/phase0/helpers.py
@@ -61,7 +61,7 @@ def create_mock_genesis_validator_deposits(num_validators, deposit_data_leaves=N
             amount=spec.MAX_DEPOSIT_AMOUNT,
             proof_of_possession=proof_of_possession,
         )
-        item = hash(deposit_data.serialize())
+        item = deposit_data.hash_tree_root()
         deposit_data_leaves.append(item)
         tree = calc_merkle_tree_from_leaves(tuple(deposit_data_leaves))
         root = get_merkle_root((tuple(deposit_data_leaves)))
@@ -180,7 +180,7 @@ def build_deposit(state,
                   amount):
     deposit_data = build_deposit_data(state, pubkey, privkey, amount)
 
-    item = hash(deposit_data.serialize())
+    item = deposit_data.hash_tree_root()
     index = len(deposit_data_leaves)
     deposit_data_leaves.append(item)
     tree = calc_merkle_tree_from_leaves(tuple(deposit_data_leaves))
diff --git a/tests/phase0/test_sanity.py b/tests/phase0/test_sanity.py
index 08c7610c0..2c13c2415 100644
--- a/tests/phase0/test_sanity.py
+++ b/tests/phase0/test_sanity.py
@@ -179,7 +179,7 @@ def test_deposit_in_block(state):
     privkey = privkeys[index]
     deposit_data = build_deposit_data(pre_state, pubkey, privkey, spec.MAX_DEPOSIT_AMOUNT)
 
-    item = hash(deposit_data.serialize())
+    item = deposit_data.hash_tree_root()
     test_deposit_data_leaves.append(item)
     tree = calc_merkle_tree_from_leaves(tuple(test_deposit_data_leaves))
     root = get_merkle_root((tuple(test_deposit_data_leaves)))
@@ -218,7 +218,7 @@ def test_deposit_top_up(state):
     deposit_data = build_deposit_data(pre_state, pubkey, privkey, amount)
 
     merkle_index = len(test_deposit_data_leaves)
-    item = hash(deposit_data.serialize())
+    item = deposit_data.hash_tree_root()
     test_deposit_data_leaves.append(item)
     tree = calc_merkle_tree_from_leaves(tuple(test_deposit_data_leaves))
     root = get_merkle_root((tuple(test_deposit_data_leaves)))