diff --git a/zebra-chain/src/block/header.rs b/zebra-chain/src/block/header.rs
index 2e87db349..473982b58 100644
--- a/zebra-chain/src/block/header.rs
+++ b/zebra-chain/src/block/header.rs
@@ -38,15 +38,12 @@ pub struct BlockHeader {
     /// [Sapling and Blossom] The root LEBS2OSP256(rt) of the Sapling note
     /// commitment tree corresponding to the final Sapling treestate of
     /// this block.
-    /// [Heartwood onward] The root of a Merkle Mountain Range tree, which
-    /// commits to various features of the chain's history, including the
-    /// Sapling commitment tree. This commitment supports the FlyClient
-    /// protocol. See ZIP-221 for details.
-    // TODO:
-    //   - replace with an unspecified HistoryRootHash type?
-    // Note that the NetworkUpgrade list is in zebra-consensus, so we can't
-    // parse this field into a HistoryRootHash enum in zebra-chain.
-    pub history_root_hash: [u8; 32],
+    /// [Heartwood activation block] All zeroes. See ZIP-221 for details.
+    /// [After Heartwood activation block] The root of a Merkle Mountain
+    /// Range tree, which commits to various features of the chain's
+    /// history, including the Sapling commitment tree. This commitment
+    /// supports the FlyClient protocol. See ZIP-221 for details.
+    pub light_client_root_hash: [u8; 32],
 
     /// The block timestamp is a Unix epoch time (UTC) when the miner
     /// started hashing the header (according to the miner).
diff --git a/zebra-chain/src/block/serialize.rs b/zebra-chain/src/block/serialize.rs
index 2824b9e21..23c7c28b4 100644
--- a/zebra-chain/src/block/serialize.rs
+++ b/zebra-chain/src/block/serialize.rs
@@ -18,7 +18,7 @@ impl ZcashSerialize for BlockHeader {
         writer.write_u32::<LittleEndian>(self.version)?;
         self.previous_block_hash.zcash_serialize(&mut writer)?;
         writer.write_all(&self.merkle_root_hash.0[..])?;
-        writer.write_all(&self.history_root_hash[..])?;
+        writer.write_all(&self.light_client_root_hash[..])?;
         // this is a truncating cast, rather than a saturating cast
         // but u32 times are valid until 2106, and our block verification time
         // checks should detect any truncation.
@@ -66,7 +66,7 @@ impl ZcashDeserialize for BlockHeader {
             version,
             previous_block_hash: BlockHeaderHash::zcash_deserialize(&mut reader)?,
             merkle_root_hash: MerkleTreeRootHash(reader.read_32_bytes()?),
-            history_root_hash: reader.read_32_bytes()?,
+            light_client_root_hash: reader.read_32_bytes()?,
             // This can't panic, because all u32 values are valid `Utc.timestamp`s
             time: Utc.timestamp(reader.read_u32::<LittleEndian>()? as i64, 0),
             difficulty_threshold: CompactDifficulty(reader.read_u32::<LittleEndian>()?),
diff --git a/zebra-chain/src/block/tests.rs b/zebra-chain/src/block/tests.rs
index df708aeec..589eedfa2 100644
--- a/zebra-chain/src/block/tests.rs
+++ b/zebra-chain/src/block/tests.rs
@@ -39,7 +39,7 @@ impl Arbitrary for BlockHeader {
                     version,
                     previous_block_hash,
                     merkle_root_hash,
-                    history_root_hash,
+                    light_client_root_hash,
                     timestamp,
                     difficulty_threshold,
                     nonce,
@@ -48,7 +48,7 @@ impl Arbitrary for BlockHeader {
                     version,
                     previous_block_hash,
                     merkle_root_hash,
-                    history_root_hash,
+                    light_client_root_hash,
                     time: Utc.timestamp(timestamp, 0),
                     difficulty_threshold,
                     nonce,