diff --git a/specs/merge/validator.md b/specs/merge/validator.md
index 6ca7c9c12..22fc3eb13 100644
--- a/specs/merge/validator.md
+++ b/specs/merge/validator.md
@@ -45,6 +45,7 @@ def get_pow_block_at_terminal_total_difficulty(pow_chain: Dict[Hash32, PowBlock]
     # `pow_chain` abstractly represents all blocks in the PoW chain
     for block in pow_chain:
         block_reached_ttd = block.total_difficulty >= TERMINAL_TOTAL_DIFFICULTY
+        # If genesis block, no parent exists so reaching TTD alone qualifies as valid terminal block
         if block_reached_ttd and block.parent_hash == Hash32():
             return block
         parent = pow_chain[block.parent_hash]