diff --git a/specs/phase1/validator.md b/specs/phase1/validator.md
index 4eadec495..7f38c6043 100644
--- a/specs/phase1/validator.md
+++ b/specs/phase1/validator.md
@@ -31,7 +31,7 @@
     - [`FullAttestation`](#fullattestation)
     - [Timing](#timing)
     - [Attestation data](#attestation-data)
-      - [Head shard root](#head-shard-root)
+      - [Shard head root](#shard-head-root)
       - [Shard transition](#shard-transition)
     - [Construct attestation](#construct-attestation)
   - [Attestation Aggregation](#attestation-aggregation)
@@ -267,9 +267,9 @@ A validator should create and broadcast the `attestation` to the associated atte
 
 *Note*: We assume that the fork choice only follows branches with valid `offset_slots` with respect to the most recent beacon state shard transition for the queried shard.
 
-##### Head shard root
+##### Shard head root
 
-Set `attestation_data.shard_head_root = hash_tree_root(shard_head_block)`.
+If `attestation_data.slot == GENESIS_SLOT`, set `attestation_data.shard_head_root = Root()`. Otherwise, set `attestation_data.shard_head_root = hash_tree_root(shard_head_block)`.
 
 ##### Shard transition