diff --git a/terraform/context.go b/terraform/context.go
index 1eaeada139..a48e46863d 100644
--- a/terraform/context.go
+++ b/terraform/context.go
@@ -362,7 +362,7 @@ func (c *Context) Apply() (*State, error) {
 		graph, err = c.Graph(&ContextGraphOpts{Validate: true})
 	} else {
 		graph, err = (&ApplyGraphBuilder{
-			Config:       c.module,
+			Module:       c.module,
 			Diff:         c.diff,
 			State:        c.state,
 			Providers:    c.providersList(),
diff --git a/terraform/graph_builder_apply.go b/terraform/graph_builder_apply.go
index d96c2d3f21..8dde58519e 100644
--- a/terraform/graph_builder_apply.go
+++ b/terraform/graph_builder_apply.go
@@ -12,8 +12,8 @@ import (
 // that aren't explicitly in the diff. There are other scenarios where the
 // diff can be deviated, so this is just one layer of protection.
 type ApplyGraphBuilder struct {
-	// Config is the root module for the graph to build.
-	Config *module.Tree
+	// Module is the root module for the graph to build.
+	Module *module.Tree
 
 	// Diff is the diff to apply.
 	Diff *Diff
@@ -42,7 +42,7 @@ func (b *ApplyGraphBuilder) Steps() []GraphTransformer {
 		// Creates all the nodes represented in the diff.
 		&DiffTransformer{
 			Diff:   b.Diff,
-			Config: b.Config,
+			Module: b.Module,
 			State:  b.State,
 		},
 
diff --git a/terraform/test-fixtures/transform-diff-basic/main.tf b/terraform/test-fixtures/transform-diff-basic/main.tf
new file mode 100644
index 0000000000..919f140bba
--- /dev/null
+++ b/terraform/test-fixtures/transform-diff-basic/main.tf
@@ -0,0 +1 @@
+resource "aws_instance" "foo" {}
diff --git a/terraform/transform_diff.go b/terraform/transform_diff.go
index c154fa7f8d..f0455f5e39 100644
--- a/terraform/transform_diff.go
+++ b/terraform/transform_diff.go
@@ -12,14 +12,14 @@ import (
 // This transform is used for example by the ApplyGraphBuilder to ensure
 // that only resources that are being modified are represented in the graph.
 //
-// Config and State is still required for the DiffTransformer for annotations
+// Module and State is still required for the DiffTransformer for annotations
 // since the Diff doesn't contain all the information required to build the
 // complete graph (such as create-before-destroy information). The graph
 // is built based on the diff first, though, ensuring that only resources
 // that are being modified are present in the graph.
 type DiffTransformer struct {
 	Diff   *Diff
-	Config *module.Tree
+	Module *module.Tree
 	State  *State
 }
 
@@ -70,7 +70,7 @@ func (t *DiffTransformer) Transform(g *Graph) error {
 	// Annotate all nodes with their config and state
 	for _, n := range nodes {
 		// Grab the configuration at this path.
-		if t := t.Config.Child(n.Addr.Path); t != nil {
+		if t := t.Module.Child(n.Addr.Path); t != nil {
 			for _, r := range t.Config().Resources {
 				// Get a resource address so we can compare
 				addr, err := parseResourceAddressConfig(r)
diff --git a/terraform/transform_diff_test.go b/terraform/transform_diff_test.go
new file mode 100644
index 0000000000..c3e3176e64
--- /dev/null
+++ b/terraform/transform_diff_test.go
@@ -0,0 +1,60 @@
+package terraform
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestDiffTransformer_nilDiff(t *testing.T) {
+	g := Graph{Path: RootModulePath}
+	tf := &DiffTransformer{}
+	if err := tf.Transform(&g); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if len(g.Vertices()) > 0 {
+		t.Fatal("graph should be empty")
+	}
+}
+
+func TestDiffTransformer(t *testing.T) {
+	g := Graph{Path: RootModulePath}
+	tf := &DiffTransformer{
+		Module: testModule(t, "transform-diff-basic"),
+		Diff: &Diff{
+			Modules: []*ModuleDiff{
+				&ModuleDiff{
+					Path: []string{"root"},
+					Resources: map[string]*InstanceDiff{
+						"aws_instance.foo": &InstanceDiff{
+							Attributes: map[string]*ResourceAttrDiff{
+								"name": &ResourceAttrDiff{
+									Old: "",
+									New: "foo",
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+	}
+	if err := tf.Transform(&g); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	actual := strings.TrimSpace(g.String())
+	expected := strings.TrimSpace(testTransformDiffBasicStr)
+	if actual != expected {
+		t.Fatalf("bad:\n\n%s", actual)
+	}
+
+	v := g.Vertices()[0].(*NodeApplyableResource)
+	if v.Config == nil {
+		t.Fatal("no config")
+	}
+}
+
+const testTransformDiffBasicStr = `
+aws_instance.foo
+`