diff --git a/dag/dag.go b/dag/dag.go
index 0026fd9fd..f8776bc51 100644
--- a/dag/dag.go
+++ b/dag/dag.go
@@ -167,7 +167,7 @@ func (g *AcyclicGraph) Walk(cb WalkFunc) error {
 	defer g.debug.BeginOperation(typeWalk, "").End("")
 
 	w := &Walker{Callback: cb, Reverse: true}
-	w.Update(&g.Graph)
+	w.Update(g)
 	return w.Wait()
 }
 
diff --git a/dag/walk.go b/dag/walk.go
index 47965764c..a74f1142a 100644
--- a/dag/walk.go
+++ b/dag/walk.go
@@ -135,7 +135,7 @@ func (w *Walker) Wait() error {
 //
 // Multiple Updates can be called in parallel. Update can be called at any
 // time during a walk.
-func (w *Walker) Update(g *Graph) {
+func (w *Walker) Update(g *AcyclicGraph) {
 	var v, e *Set
 	if g != nil {
 		v, e = g.vertices, g.edges
diff --git a/dag/walk_test.go b/dag/walk_test.go
index 5843ca64b..628ae6f64 100644
--- a/dag/walk_test.go
+++ b/dag/walk_test.go
@@ -9,7 +9,7 @@ import (
 )
 
 func TestWalker_basic(t *testing.T) {
-	var g Graph
+	var g AcyclicGraph
 	g.Add(1)
 	g.Add(2)
 	g.Connect(BasicEdge(1, 2))
@@ -34,7 +34,7 @@ func TestWalker_basic(t *testing.T) {
 }
 
 func TestWalker_updateNilGraph(t *testing.T) {
-	var g Graph
+	var g AcyclicGraph
 	g.Add(1)
 	g.Add(2)
 	g.Connect(BasicEdge(1, 2))
@@ -54,7 +54,7 @@ func TestWalker_updateNilGraph(t *testing.T) {
 }
 
 func TestWalker_error(t *testing.T) {
-	var g Graph
+	var g AcyclicGraph
 	g.Add(1)
 	g.Add(2)
 	g.Add(3)
@@ -94,7 +94,7 @@ func TestWalker_error(t *testing.T) {
 func TestWalker_newVertex(t *testing.T) {
 	// Run it a bunch of times since it is timing dependent
 	for i := 0; i < 50; i++ {
-		var g Graph
+		var g AcyclicGraph
 		g.Add(1)
 		g.Add(2)
 		g.Connect(BasicEdge(1, 2))
@@ -130,7 +130,7 @@ func TestWalker_newVertex(t *testing.T) {
 func TestWalker_removeVertex(t *testing.T) {
 	// Run it a bunch of times since it is timing dependent
 	for i := 0; i < 50; i++ {
-		var g Graph
+		var g AcyclicGraph
 		g.Add(1)
 		g.Add(2)
 		g.Connect(BasicEdge(1, 2))
@@ -170,7 +170,7 @@ func TestWalker_removeVertex(t *testing.T) {
 func TestWalker_newEdge(t *testing.T) {
 	// Run it a bunch of times since it is timing dependent
 	for i := 0; i < 50; i++ {
-		var g Graph
+		var g AcyclicGraph
 		g.Add(1)
 		g.Add(2)
 		g.Connect(BasicEdge(1, 2))
@@ -211,7 +211,7 @@ func TestWalker_newEdge(t *testing.T) {
 func TestWalker_removeEdge(t *testing.T) {
 	// Run it a bunch of times since it is timing dependent
 	for i := 0; i < 50; i++ {
-		var g Graph
+		var g AcyclicGraph
 		g.Add(1)
 		g.Add(2)
 		g.Add(3)