diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index eaceec6ac1..0b2ccf0282 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -1310,7 +1310,7 @@ The initial deployment phases of Ethereum 2.0 are implemented without consensus
 
 ### Deposit arguments
 
-The deposit contract has a single `deposit` function which takes as argument a SimpleSerialize'd `DepositData`.
+The deposit contract has a single `deposit` function which takes as argument the `DepositData` elements.
 
 ### Withdrawal credentials
 
@@ -1345,7 +1345,7 @@ For convenience, we provide the interface to the contract here:
 
 * `__init__()`: initializes the contract
 * `get_deposit_root() -> bytes32`: returns the current root of the deposit tree
-* `deposit(bytes[512])`: adds a deposit instance to the deposit tree, incorporating the input argument and the value transferred in the given call. Note: the amount of value transferred *must* be within `MIN_DEPOSIT_AMOUNT` and `MAX_DEPOSIT_AMOUNT`, inclusive. Each of these constants are specified in units of Gwei.
+* `deposit(pubkey: bytes[48], withdrawal_credentials: bytes[32], signature: bytes[96])`: adds a deposit instance to the deposit tree, incorporating the input arguments and the value transferred in the given call. Note: the amount of value transferred *must* be within `MIN_DEPOSIT_AMOUNT` and `MAX_DEPOSIT_AMOUNT`, inclusive. Each of these constants are specified in units of Gwei.
 
 ## On genesis
 
@@ -2127,7 +2127,7 @@ def process_deposit(state: BeaconState, deposit: Deposit) -> None:
 
     # Verify the Merkle branch
     merkle_branch_is_valid = verify_merkle_branch(
-        leaf=hash(serialize(deposit.data)),  # 48 + 32 + 8 + 96 = 184 bytes serialization
+        leaf=hash_tree_root(deposit.data),
         proof=deposit.proof,
         depth=DEPOSIT_CONTRACT_TREE_DEPTH,
         index=deposit.index,
diff --git a/specs/validator/0_beacon-chain-validator.md b/specs/validator/0_beacon-chain-validator.md
index 632bf2b620..966e238ab9 100644
--- a/specs/validator/0_beacon-chain-validator.md
+++ b/specs/validator/0_beacon-chain-validator.md
@@ -101,11 +101,10 @@ In phase 0, all incoming validator deposits originate from the Ethereum 1.0 PoW
 To submit a deposit:
 
 * Pack the validator's [initialization parameters](#initialization) into `deposit_data`, a [`DepositData`](../core/0_beacon-chain.md#depositdata) SSZ object.
-* Let `proof_of_possession` be the result of `bls_sign` of the `signing_root(deposit_data)` with `domain=DOMAIN_DEPOSIT`.
-* Set `deposit_data.proof_of_possession = proof_of_possession`.
 * Let `amount` be the amount in Gwei to be deposited by the validator where `MIN_DEPOSIT_AMOUNT <= amount <= MAX_DEPOSIT_AMOUNT`.
 * Set `deposit_data.amount = amount`.
-* Send a transaction on the Ethereum 1.0 chain to `DEPOSIT_CONTRACT_ADDRESS` executing `deposit(deposit_input: bytes[512])` along with `serialize(deposit_data)` as the singular `bytes` input along with a deposit of `amount` Gwei.
+* Let `signature` be the result of `bls_sign` of the `signing_root(deposit_data)` with `domain=DOMAIN_DEPOSIT`.
+* Send a transaction on the Ethereum 1.0 chain to `DEPOSIT_CONTRACT_ADDRESS` executing `def deposit(pubkey: bytes[48], withdrawal_credentials: bytes[32], signature: bytes[96])` along with a deposit of `amount` Gwei.
 
 _Note_: Deposits made for the same `pubkey` are treated as for the same validator. A singular `Validator` will be added to `state.validator_registry` with each additional deposit amount added to the validator's balance. A validator can only be activated when total deposits for the validator pubkey meet or exceed `MAX_DEPOSIT_AMOUNT`.
 
diff --git a/test_libs/pyspec/tests/helpers.py b/test_libs/pyspec/tests/helpers.py
index 44d2dcb4d6..3f18669179 100644
--- a/test_libs/pyspec/tests/helpers.py
+++ b/test_libs/pyspec/tests/helpers.py
@@ -80,7 +80,7 @@ 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)))
@@ -208,7 +208,7 @@ 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/test_libs/pyspec/tests/test_sanity.py b/test_libs/pyspec/tests/test_sanity.py
index 29333a7ada..5d0401c9cb 100644
--- a/test_libs/pyspec/tests/test_sanity.py
+++ b/test_libs/pyspec/tests/test_sanity.py
@@ -236,7 +236,7 @@ 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)))
@@ -275,7 +275,7 @@ 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)))