diff --git a/auditing.go b/auditing.go
index 17da959..065564c 100644
--- a/auditing.go
+++ b/auditing.go
@@ -115,19 +115,19 @@ func hashChildren (left ct.MerkleTreeNode, right ct.MerkleTreeNode) ct.MerkleTre
 	return hasher.Sum(nil)
 }
 
-type MerkleBuilder struct {
+type MerkleTreeBuilder struct {
 	stack		[]ct.MerkleTreeNode
 	size		uint64 // number of hashes added so far
 }
 
-func ResumedMerkleBuilder (hashes []ct.MerkleTreeNode, size uint64) *MerkleBuilder {
-	return &MerkleBuilder{
+func ResumedMerkleTreeBuilder (hashes []ct.MerkleTreeNode, size uint64) *MerkleTreeBuilder {
+	return &MerkleTreeBuilder{
 		stack: hashes,
 		size: size,
 	}
 }
 
-func (builder *MerkleBuilder) Add (hash ct.MerkleTreeNode) {
+func (builder *MerkleTreeBuilder) Add (hash ct.MerkleTreeNode) {
 	builder.stack = append(builder.stack, hash)
 	builder.size++
 	size := builder.size
@@ -139,9 +139,9 @@ func (builder *MerkleBuilder) Add (hash ct.MerkleTreeNode) {
 	}
 }
 
-func (builder *MerkleBuilder) Finish () ct.MerkleTreeNode {
+func (builder *MerkleTreeBuilder) Finish () ct.MerkleTreeNode {
 	if len(builder.stack) == 0 {
-		panic("MerkleBuilder.Finish called on an empty tree")
+		panic("MerkleTreeBuilder.Finish called on an empty tree")
 	}
 	for len(builder.stack) > 1 {
 		left, right := builder.stack[len(builder.stack)-2], builder.stack[len(builder.stack)-1]
diff --git a/cmd/common.go b/cmd/common.go
index 49f9612..7fd568c 100644
--- a/cmd/common.go
+++ b/cmd/common.go
@@ -159,7 +159,7 @@ func Main (argStateDir string, processCallback ctwatch.ProcessCallback) {
 		}
 
 		if latestSTH.TreeSize > startIndex {
-			var merkleBuilder *ctwatch.MerkleBuilder
+			var treeBuilder *ctwatch.MerkleTreeBuilder
 			if prevSTH != nil {
 				valid, nodes, err := scanner.CheckConsistency(prevSTH, latestSTH)
 				if err != nil {
@@ -173,18 +173,18 @@ func Main (argStateDir string, processCallback ctwatch.ProcessCallback) {
 					continue
 				}
 
-				merkleBuilder = ctwatch.ResumedMerkleBuilder(nodes, prevSTH.TreeSize)
+				treeBuilder = ctwatch.ResumedMerkleTreeBuilder(nodes, prevSTH.TreeSize)
 			} else {
-				merkleBuilder = &ctwatch.MerkleBuilder{}
+				treeBuilder = &ctwatch.MerkleTreeBuilder{}
 			}
 
-			if err := scanner.Scan(int64(startIndex), int64(latestSTH.TreeSize), processCallback, merkleBuilder); err != nil {
+			if err := scanner.Scan(int64(startIndex), int64(latestSTH.TreeSize), processCallback, treeBuilder); err != nil {
 				fmt.Fprintf(os.Stderr, "%s: Error scanning log: %s: %s\n", os.Args[0], logUri, err)
 				exitCode = 1
 				continue
 			}
 
-			rootHash := merkleBuilder.Finish()
+			rootHash := treeBuilder.Finish()
 			if !bytes.Equal(rootHash, latestSTH.SHA256RootHash[:]) {
 				fmt.Fprintf(os.Stderr, "%s: %s: Validation of log entries failed - calculated tree root (%x) does not match signed tree root (%s)\n", os.Args[0], logUri, rootHash, latestSTH.SHA256RootHash)
 				exitCode = 1
diff --git a/scanner.go b/scanner.go
index 338a92e..7345008 100644
--- a/scanner.go
+++ b/scanner.go
@@ -77,7 +77,7 @@ func (s *Scanner) processerJob(id int, entries <-chan ct.LogEntry, processCert P
 	wg.Done()
 }
 
-func (s *Scanner) fetch(r fetchRange, entries chan<- ct.LogEntry, merkleBuilder *MerkleBuilder) {
+func (s *Scanner) fetch(r fetchRange, entries chan<- ct.LogEntry, treeBuilder *MerkleTreeBuilder) {
 	success := false
 	// TODO(alcutter): give up after a while:
 	for !success {
@@ -88,8 +88,8 @@ func (s *Scanner) fetch(r fetchRange, entries chan<- ct.LogEntry, merkleBuilder
 			continue
 		}
 		for _, logEntry := range logEntries {
-			if merkleBuilder != nil {
-				merkleBuilder.Add(hashLeaf(logEntry.LeafBytes))
+			if treeBuilder != nil {
+				treeBuilder.Add(hashLeaf(logEntry.LeafBytes))
 			}
 			logEntry.Index = r.start
 			entries <- logEntry
@@ -207,7 +207,7 @@ func (s *Scanner) CheckConsistency(first *ct.SignedTreeHead, second *ct.SignedTr
 	return valid, builderNodes, nil
 }
 
-func (s *Scanner) Scan(startIndex int64, endIndex int64, processCert ProcessCallback, merkleBuilder *MerkleBuilder) error {
+func (s *Scanner) Scan(startIndex int64, endIndex int64, processCert ProcessCallback, treeBuilder *MerkleTreeBuilder) error {
 	s.Log("Starting scan...");
 
 	s.certsProcessed = 0
@@ -256,7 +256,7 @@ func (s *Scanner) Scan(startIndex int64, endIndex int64, processCert ProcessCall
 	*/
 	for start := startIndex; start < int64(endIndex); {
 		end := min(start+int64(s.opts.BatchSize), int64(endIndex)) - 1
-		s.fetch(fetchRange{start, end}, jobs, merkleBuilder)
+		s.fetch(fetchRange{start, end}, jobs, treeBuilder)
 		start = end + 1
 	}
 	close(jobs)