diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index ab9bde4e2..b5f208488 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -471,8 +471,6 @@ The types are defined topologically to aid in facilitating an executable version
 {
     # Branch in the deposit tree
     'proof': ['bytes32', DEPOSIT_CONTRACT_TREE_DEPTH],
-    # Index in the deposit tree
-    'index': 'uint64',
     # Data
     'data': DepositData,
 }
@@ -1761,12 +1759,11 @@ def process_deposit(state: BeaconState, deposit: Deposit) -> None:
         leaf=hash_tree_root(deposit.data),
         proof=deposit.proof,
         depth=DEPOSIT_CONTRACT_TREE_DEPTH,
-        index=deposit.index,
+        index=state.deposit_index,
         root=state.latest_eth1_data.deposit_root,
     )
 
     # Deposits must be processed in order
-    assert deposit.index == state.deposit_index
     state.deposit_index += 1
 
     pubkey = deposit.data.pubkey
diff --git a/test_libs/pyspec/eth2spec/test/block_processing/test_process_deposit.py b/test_libs/pyspec/eth2spec/test/block_processing/test_process_deposit.py
index 336af3bf7..0ef2e509a 100644
--- a/test_libs/pyspec/eth2spec/test/block_processing/test_process_deposit.py
+++ b/test_libs/pyspec/eth2spec/test/block_processing/test_process_deposit.py
@@ -1,9 +1,13 @@
 import eth2spec.phase0.spec as spec
 from eth2spec.phase0.spec import process_deposit
 from eth2spec.test.context import spec_state_test, expect_assertion_error, always_bls
-from eth2spec.test.helpers.deposits import prepare_state_and_deposit, sign_deposit_data
+from eth2spec.test.helpers.deposits import (
+    build_deposit,
+    prepare_state_and_deposit,
+    sign_deposit_data,
+)
 from eth2spec.test.helpers.state import get_balance
-from eth2spec.test.helpers.keys import privkeys
+from eth2spec.test.helpers.keys import privkeys, pubkeys
 
 
 def run_deposit_processing(state, deposit, validator_index, valid=True, effective=True):
@@ -18,9 +22,6 @@ def run_deposit_processing(state, deposit, validator_index, valid=True, effectiv
     pre_balance = 0
     if validator_index < pre_validator_count:
         pre_balance = get_balance(state, validator_index)
-    else:
-        # if it is a new validator, it should be right at the end of the current registry.
-        assert validator_index == pre_validator_count
 
     yield 'pre', state
     yield 'deposit', deposit
@@ -107,6 +108,44 @@ def test_wrong_index(state):
     yield from run_deposit_processing(state, deposit, validator_index, valid=False)
 
 
+@spec_state_test
+def test_wrong_deposit_for_deposit_count(state):
+    deposit_data_leaves = [spec.ZERO_HASH] * len(state.validator_registry)
+
+    # build root for deposit_1
+    index_1 = len(deposit_data_leaves)
+    pubkey_1 = pubkeys[index_1]
+    privkey_1 = privkeys[index_1]
+    deposit_1, root_1, deposit_data_leaves = build_deposit(
+        state,
+        deposit_data_leaves,
+        pubkey_1,
+        privkey_1,
+        spec.MAX_EFFECTIVE_BALANCE,
+        signed=True,
+    )
+    deposit_count_1 = len(deposit_data_leaves)
+
+    # build root for deposit_2
+    index_2 = len(deposit_data_leaves)
+    pubkey_2 = pubkeys[index_2]
+    privkey_2 = privkeys[index_2]
+    deposit_2, root_2, deposit_data_leaves = build_deposit(
+        state,
+        deposit_data_leaves,
+        pubkey_2,
+        privkey_2,
+        spec.MAX_EFFECTIVE_BALANCE,
+        signed=True,
+    )
+
+    # state has root for deposit_2 but is at deposit_count for deposit_1
+    state.latest_eth1_data.deposit_root = root_2
+    state.latest_eth1_data.deposit_count = deposit_count_1
+
+    yield from run_deposit_processing(state, deposit_2, index_2, valid=False)
+
+
 # TODO: test invalid signature