diff --git a/src/blockchain.erl b/src/blockchain.erl
index 0596b4fb47..0f68605f00 100644
--- a/src/blockchain.erl
+++ b/src/blockchain.erl
@@ -1468,6 +1468,8 @@ build(Height, Blockchain, N, Acc) ->
 ) ->
     [H, ...] when H :: blockchain_block:hash().
 build_hash_chain(StopHash, StartBlock, #blockchain{db=DB}, CF) ->
+    %% TODO Can the following deserialization step be eliminated, if we
+    %%      maintain a rocksdb CF of ChildHash->ParentHash.
     Parents =
         maps:from_list(
             data_stream:pmap_to_bag(