diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index b7cdae168..dfe7f3fa3 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -666,7 +666,7 @@ def deposit(deposit_input: bytes[2048]):
     assert msg.value >= as_wei_value(MIN_DEPOSIT, "ether")
     assert msg.value <= as_wei_value(MAX_DEPOSIT, "ether")
 
-    index: uint256 = self.deposit_tree_index + TWO_TO_POWER_OF_TREE_DEPTH
+    index: uint256 = self.deposit_count + TWO_TO_POWER_OF_TREE_DEPTH
     msg_gwei_bytes8: bytes[8] = slice(concat("", convert(msg.value / GWEI_PER_ETH, bytes32)), start=24, len=8)
     timestamp_bytes8: bytes[8] = slice(concat("", convert(block.timestamp, bytes32)), start=24, len=8)
     deposit_data: bytes[2064] = concat(msg_gwei_bytes8, timestamp_bytes8, deposit_input)
@@ -679,7 +679,7 @@ def deposit(deposit_input: bytes[2048]):
         index /= 2
         self.deposit_tree[index] = sha3(concat(self.deposit_tree[index * 2], self.deposit_tree[index * 2 + 1]))
 
-    self.deposit_tree_index += 1
+    self.deposit_count += 1
     if msg.value == as_wei_value(MAX_DEPOSIT, "ether"):
         self.full_deposit_count += 1
         if self.full_deposit_count == CHAIN_START_FULL_DEPOSIT_THRESHOLD: