diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index 2f5b1b3f9..fc1ad3323 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -358,6 +358,7 @@ Unless otherwise indicated, code appearing in `this style` is to be interpreted
     # Receipt Merkle branch
     'merkle_branch': '[hash32]',
     # Merkle tree index
+    # referred to as `deposit_count` in the Ethereum 1.0 deposit contract
     'merkle_tree_index': 'uint64',
     # Deposit data
     'deposit_data': DepositData,