diff --git a/sharding/collation.go b/sharding/collation.go
index 245b1e8e0..5528453e4 100644
--- a/sharding/collation.go
+++ b/sharding/collation.go
@@ -56,10 +56,10 @@ func NewCollationHeader(shardID *big.Int, chunkRoot *common.Hash, period *big.In
 	return &CollationHeader{data}
 }
 
-// Hash takes the keccak256 of the collation header's contents.
+// Hash takes the keccak256 of the collation header's data contents.
 func (h *CollationHeader) Hash() (hash common.Hash) {
 	hw := sha3.NewKeccak256()
-	rlp.Encode(hw, h)
+	rlp.Encode(hw, h.data)
 	hw.Sum(hash[:0])
 	return hash
 }