diff --git a/graph.go b/graph.go
index 09770f8e30..34adec1b04 100644
--- a/graph.go
+++ b/graph.go
@@ -273,7 +273,7 @@ func (graph *Graph) Delete(name string) error {
 // Map returns a list of all images in the graph, addressable by ID.
 func (graph *Graph) Map() (map[string]*Image, error) {
 	images := make(map[string]*Image)
-	err := graph.WalkAll(func(image *Image) {
+	err := graph.walkAll(func(image *Image) {
 		images[image.ID] = image
 	})
 	if err != nil {
@@ -282,9 +282,9 @@ func (graph *Graph) Map() (map[string]*Image, error) {
 	return images, nil
 }
 
-// WalkAll iterates over each image in the graph, and passes it to a handler.
+// walkAll iterates over each image in the graph, and passes it to a handler.
 // The walking order is undetermined.
-func (graph *Graph) WalkAll(handler func(*Image)) error {
+func (graph *Graph) walkAll(handler func(*Image)) error {
 	files, err := ioutil.ReadDir(graph.Root)
 	if err != nil {
 		return err
@@ -306,7 +306,7 @@ func (graph *Graph) WalkAll(handler func(*Image)) error {
 // If an image has no children, it will not have an entry in the table.
 func (graph *Graph) ByParent() (map[string][]*Image, error) {
 	byParent := make(map[string][]*Image)
-	err := graph.WalkAll(func(image *Image) {
+	err := graph.walkAll(func(image *Image) {
 		parent, err := graph.Get(image.Parent)
 		if err != nil {
 			return
@@ -328,7 +328,7 @@ func (graph *Graph) Heads() (map[string]*Image, error) {
 	if err != nil {
 		return nil, err
 	}
-	err = graph.WalkAll(func(image *Image) {
+	err = graph.walkAll(func(image *Image) {
 		// If it's not in the byParent lookup table, then
 		// it's not a parent -> so it's a head!
 		if _, exists := byParent[image.ID]; !exists {