diff --git a/eth2/beacon/on_startup.py b/eth2/beacon/on_startup.py
index ebb1c624d8..aa112f681a 100644
--- a/eth2/beacon/on_startup.py
+++ b/eth2/beacon/on_startup.py
@@ -119,6 +119,7 @@ def get_genesis_beacon_state(*,
         # Ethereum 1.0 chain data
         latest_eth1_data=latest_eth1_data,
         eth1_data_votes=(),
+        deposit_index=len(genesis_validator_deposits),
     )
 
     # Process initial deposits
diff --git a/eth2/beacon/types/states.py b/eth2/beacon/types/states.py
index a32c2ae6e7..9162c40f7a 100644
--- a/eth2/beacon/types/states.py
+++ b/eth2/beacon/types/states.py
@@ -87,6 +87,7 @@ class BeaconState(rlp.Serializable):
         # Ethereum 1.0 chain
         ('latest_eth1_data', Eth1Data),
         ('eth1_data_votes', CountableList(Eth1DataVote)),
+        ('deposit_index', uint64),
     ]
 
     def __init__(
@@ -122,7 +123,8 @@ def __init__(
             latest_attestations: Sequence[PendingAttestationRecord],
             # Ethereum 1.0 chain
             latest_eth1_data: Eth1Data,
-            eth1_data_votes: Sequence[Eth1DataVote]) -> None:
+            eth1_data_votes: Sequence[Eth1DataVote],
+            deposit_index: int) -> None:
         if len(validator_registry) != len(validator_balances):
             raise ValueError(
                 "The length of validator_registry and validator_balances should be the same."
@@ -159,6 +161,7 @@ def __init__(
             # Ethereum 1.0 chain
             latest_eth1_data=latest_eth1_data,
             eth1_data_votes=eth1_data_votes,
+            deposit_index=deposit_index,
         )
 
     def __repr__(self) -> str:
@@ -244,6 +247,7 @@ def create_filled_state(cls,
             # Ethereum 1.0 chain data
             latest_eth1_data=Eth1Data.create_empty_data(),
             eth1_data_votes=(),
+            deposit_index=len(activated_genesis_validators),
         )
 
     def update_validator_registry(self,
diff --git a/tests/eth2/beacon/conftest.py b/tests/eth2/beacon/conftest.py
index 3f9fa3d782..9f379adfd8 100644
--- a/tests/eth2/beacon/conftest.py
+++ b/tests/eth2/beacon/conftest.py
@@ -169,6 +169,7 @@ def sample_beacon_state_params(sample_fork_params, sample_eth1_data_params):
         'batched_block_roots': (),
         'latest_eth1_data': Eth1Data(**sample_eth1_data_params),
         'eth1_data_votes': (),
+        'deposit_index': 0,
     }
 
 
diff --git a/tests/eth2/beacon/test_on_startup.py b/tests/eth2/beacon/test_on_startup.py
index 7984313a2a..90b8fcc73e 100644
--- a/tests/eth2/beacon/test_on_startup.py
+++ b/tests/eth2/beacon/test_on_startup.py
@@ -76,7 +76,7 @@ def test_get_genesis_beacon_state(
 
     validator_count = 5
 
-    genesis_validator_deposits = (
+    genesis_validator_deposits = tuple(
         Deposit(
             branch=(
                 b'\x11' * 32
@@ -171,5 +171,6 @@ def test_get_genesis_beacon_state(
     # Ethereum 1.0 chain data
     assert state.latest_eth1_data == latest_eth1_data
     assert len(state.eth1_data_votes) == 0
+    assert state.deposit_index == len(genesis_validator_deposits)
 
     assert state.validator_registry[0].is_active(genesis_epoch)