diff --git a/core/state/database.go b/core/state/database.go
index a2d01f168c..a43485bcc9 100644
--- a/core/state/database.go
+++ b/core/state/database.go
@@ -126,13 +126,14 @@ type Trie interface {
 	// be created with new root and updated trie database for following usage
 	Commit(collectLeaf bool) (common.Hash, *trienode.NodeSet, error)
 
-	// CommitAndObtainAccessList does the same thing as Commit and returns an
-	// access list map of trie nodes read from the database.
-	CommitAndObtainAccessList(collectLeaf bool) (common.Hash, *trienode.NodeSet, map[string][]byte, error)
-
-	// AccessList returns a map of trie node read from the database.
+	// AccessList returns a map of path->blob containing all trie nodes that have
+	// been accessed.
 	AccessList() map[string][]byte
 
+	// CommitAndObtainAccessList does the same thing as Commit, but also returns
+	// the access list of the trie.
+	CommitAndObtainAccessList(collectLeaf bool) (common.Hash, *trienode.NodeSet, map[string][]byte, error)
+
 	// NodeIterator returns an iterator that returns nodes of the trie. Iteration
 	// starts at the key after the given start key. And error will be returned
 	// if fails to create node iterator.
diff --git a/core/state/state_witness.go b/core/state/state_witness.go
index e83e46dc81..7cc9833b79 100644
--- a/core/state/state_witness.go
+++ b/core/state/state_witness.go
@@ -2,7 +2,6 @@ package state
 
 import (
 	"bytes"
-	"crypto/sha256"
 	"fmt"
 	"sort"
 
@@ -317,16 +316,6 @@ func (w *Witness) PrettyPrint() string {
 	return b.String()
 }
 
-// Hash returns the sha256 hash of a witness
-func (w *Witness) Hash() common.Hash {
-	res, err := rlp.EncodeToBytes(w.sortedWitness())
-	if err != nil {
-		panic(err)
-	}
-
-	return common.Hash(sha256.Sum256(res[:]))
-}
-
 // NewWitness returns a new witness object.
 func NewWitness(root common.Hash) *Witness {
 	return &Witness{
diff --git a/core/state/statedb.go b/core/state/statedb.go
index 93d267a533..6f4373ab99 100644
--- a/core/state/statedb.go
+++ b/core/state/statedb.go
@@ -918,13 +918,13 @@ func (s *StateDB) IntermediateRoot(deleteEmptyObjects bool) common.Hash {
 	// Finalise all the dirty storage states and write them into the tries
 	s.Finalise(deleteEmptyObjects)
 
-        // If there was a trie prefetcher operating, it gets aborted and irrevocably
-        // modified after we start retrieving tries. Remove it from the statedb after
-        // this round of use.
-        //
-        // This is weird pre-byzantium since the first tx runs with a prefetcher and
-        // the remainder without, but pre-byzantium even the initial prefetcher is
-        // useless, so no sleep lost.
+	// If there was a trie prefetcher operating, it gets aborted and irrevocably
+	// modified after we start retrieving tries. Remove it from the statedb after
+	// this round of use.
+	//
+	// This is weird pre-byzantium since the first tx runs with a prefetcher and
+	// the remainder without, but pre-byzantium even the initial prefetcher is
+	// useless, so no sleep lost.
 	prefetcher := s.prefetcher
 	if s.prefetcher != nil {
 		defer func() {
@@ -1412,7 +1412,6 @@ func (s *StateDB) Commit(block uint64, deleteEmptyObjects bool) (common.Hash, er
 	s.storagesOrigin = make(map[common.Address]map[common.Hash][]byte)
 	s.stateObjectsDirty = make(map[common.Address]struct{})
 	s.stateObjectsDestruct = make(map[common.Address]*types.StateAccount)
-
 	return root, nil
 }
 
diff --git a/core/types/block.go b/core/types/block.go
index 1a357baa3a..eef7970919 100644
--- a/core/types/block.go
+++ b/core/types/block.go
@@ -329,6 +329,18 @@ func (b *Block) EncodeRLP(w io.Writer) error {
 	})
 }
 
+// EncodeRLPWithZeroRoot encodes a block (with header state root set to 0x00...0) to RLP
+func (b *Block) EncodeRLPWithZeroRoot(w io.Writer) error {
+	old := b.header.Root
+	b.header.Root = common.Hash{}
+	err := b.EncodeRLP(w)
+	b.header.Root = old
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
 // Body returns the non-header content of the block.
 // Note the returned data is not an independent copy.
 func (b *Block) Body() *Body {