diff --git a/helper/schema/field_reader.go b/helper/schema/field_reader.go
index 187e79bee..6c6e0d5a4 100644
--- a/helper/schema/field_reader.go
+++ b/helper/schema/field_reader.go
@@ -9,7 +9,26 @@ import (
 // the proper typed representation. ResourceData uses this to query data
 // out of multiple sources: config, state, diffs, etc.
 type FieldReader interface {
-	ReadField([]string, *Schema) (interface{}, bool, bool, error)
+	ReadField([]string, *Schema) (FieldReadResult, error)
+}
+
+// FieldReadResult encapsulates all the resulting data from reading
+// a field.
+type FieldReadResult struct {
+	// Value is the actual read value. NegValue is the _negative_ value
+	// or the items that should be removed (if they existed). NegValue
+	// doesn't make sense for primitives but is important for any
+	// container types such as maps, sets, lists.
+	Value    interface{}
+	NegValue interface{}
+
+	// Exists is true if the field was found in the data. False means
+	// it wasn't found if there was no error.
+	Exists bool
+
+	// Computed is true if the field was found but the value
+	// is computed.
+	Computed bool
 }
 
 // readListField is a generic method for reading a list field out of a
@@ -17,21 +36,24 @@ type FieldReader interface {
 // "foo.#" for a list "foo" and that the indexes are "foo.0", "foo.1", etc.
 // after that point.
 func readListField(
-	r FieldReader, k string, schema *Schema) (interface{}, bool, bool, error) {
+	r FieldReader, k string, schema *Schema) (FieldReadResult, error) {
 	// Get the number of elements in the list
-	countRaw, countOk, countComputed, err := r.ReadField(
-		[]string{k + ".#"}, &Schema{Type: TypeInt})
+	countResult, err := r.ReadField([]string{k + ".#"}, &Schema{Type: TypeInt})
 	if err != nil {
-		return nil, false, false, err
+		return FieldReadResult{}, err
 	}
-	if !countOk {
+	if !countResult.Exists {
 		// No count, means we have no list
-		countRaw = 0
+		countResult.Value = 0
 	}
 
 	// If we have an empty list, then return an empty list
-	if countComputed || countRaw.(int) == 0 {
-		return []interface{}{}, true, countComputed, nil
+	if countResult.Computed || countResult.Value.(int) == 0 {
+		return FieldReadResult{
+			Value:    []interface{}{},
+			Exists:   true,
+			Computed: countResult.Computed,
+		}, nil
 	}
 
 	// Get the schema for the elements
@@ -47,24 +69,27 @@ func readListField(
 	}
 
 	// Go through each count, and get the item value out of it
-	result := make([]interface{}, countRaw.(int))
+	result := make([]interface{}, countResult.Value.(int))
 	for i, _ := range result {
 		is := strconv.FormatInt(int64(i), 10)
-		raw, ok, _, err := r.ReadField([]string{k, is}, elemSchema)
+		rawResult, err := r.ReadField([]string{k, is}, elemSchema)
 		if err != nil {
-			return nil, false, false, err
+			return FieldReadResult{}, err
 		}
-		if !ok {
+		if !rawResult.Exists {
 			// This should never happen, because by the time the data
 			// gets to the FieldReaders, all the defaults should be set by
 			// Schema.
-			raw = nil
+			rawResult.Value = nil
 		}
 
-		result[i] = raw
+		result[i] = rawResult.Value
 	}
 
-	return result, true, false, nil
+	return FieldReadResult{
+		Value:  result,
+		Exists: true,
+	}, nil
 }
 
 // readObjectField is a generic method for reading objects out of FieldReaders
@@ -73,21 +98,24 @@ func readListField(
 func readObjectField(
 	r FieldReader,
 	k string,
-	schema map[string]*Schema) (interface{}, bool, bool, error) {
+	schema map[string]*Schema) (FieldReadResult, error) {
 	result := make(map[string]interface{})
 	for field, schema := range schema {
-		v, ok, _, err := r.ReadField([]string{k, field}, schema)
+		rawResult, err := r.ReadField([]string{k, field}, schema)
 		if err != nil {
-			return nil, false, false, err
+			return FieldReadResult{}, err
 		}
-		if !ok {
+		if !rawResult.Exists {
 			continue
 		}
 
-		result[field] = v
+		result[field] = rawResult.Value
 	}
 
-	return result, true, false, nil
+	return FieldReadResult{
+		Value:  result,
+		Exists: true,
+	}, nil
 }
 
 func stringToPrimitive(
diff --git a/helper/schema/field_reader_config.go b/helper/schema/field_reader_config.go
index ff418287b..146aaef6e 100644
--- a/helper/schema/field_reader_config.go
+++ b/helper/schema/field_reader_config.go
@@ -15,7 +15,7 @@ type ConfigFieldReader struct {
 }
 
 func (r *ConfigFieldReader) ReadField(
-	address []string, schema *Schema) (interface{}, bool, bool, error) {
+	address []string, schema *Schema) (FieldReadResult, error) {
 	k := strings.Join(address, ".")
 
 	switch schema.Type {
@@ -38,10 +38,10 @@ func (r *ConfigFieldReader) ReadField(
 	}
 }
 
-func (r *ConfigFieldReader) readMap(k string) (interface{}, bool, bool, error) {
+func (r *ConfigFieldReader) readMap(k string) (FieldReadResult, error) {
 	mraw, ok := r.Config.Get(k)
 	if !ok {
-		return nil, false, false, nil
+		return FieldReadResult{}, nil
 	}
 
 	result := make(map[string]interface{})
@@ -64,52 +64,66 @@ func (r *ConfigFieldReader) readMap(k string) (interface{}, bool, bool, error) {
 		panic(fmt.Sprintf("unknown type: %#v", mraw))
 	}
 
-	return result, true, false, nil
+	return FieldReadResult{
+		Value:  result,
+		Exists: true,
+	}, nil
 }
 
 func (r *ConfigFieldReader) readPrimitive(
-	k string, schema *Schema) (interface{}, bool, bool, error) {
+	k string, schema *Schema) (FieldReadResult, error) {
 	raw, ok := r.Config.Get(k)
 	if !ok {
-		return nil, false, false, nil
+		return FieldReadResult{}, nil
 	}
 
 	var result string
 	if err := mapstructure.WeakDecode(raw, &result); err != nil {
-		return nil, false, false, err
+		return FieldReadResult{}, err
 	}
 
 	computed := r.Config.IsComputed(k)
 	returnVal, err := stringToPrimitive(result, computed, schema)
 	if err != nil {
-		return nil, false, false, err
+		return FieldReadResult{}, err
 	}
 
-	return returnVal, true, computed, nil
+	return FieldReadResult{
+		Value:    returnVal,
+		Exists:   true,
+		Computed: computed,
+	}, nil
 }
 
 func (r *ConfigFieldReader) readSet(
-	k string, schema *Schema) (interface{}, bool, bool, error) {
-	raw, ok, computed, err := readListField(r, k, schema)
+	k string, schema *Schema) (FieldReadResult, error) {
+	raw, err := readListField(r, k, schema)
 	if err != nil {
-		return nil, false, false, err
+		return FieldReadResult{}, err
 	}
-	if !ok {
-		return nil, false, false, nil
+	if !raw.Exists {
+		return FieldReadResult{}, nil
 	}
 
 	// Create the set that will be our result
 	set := &Set{F: schema.Set}
 
 	// If the list is computed, the set is necessarilly computed
-	if computed {
-		return set, true, computed, nil
+	if raw.Computed {
+		return FieldReadResult{
+			Value:    set,
+			Exists:   true,
+			Computed: raw.Computed,
+		}, nil
 	}
 
 	// Build up the set from the list elements
-	for _, v := range raw.([]interface{}) {
+	for _, v := range raw.Value.([]interface{}) {
 		set.Add(v)
 	}
 
-	return set, true, false, nil
+	return FieldReadResult{
+		Value:  set,
+		Exists: true,
+	}, nil
 }
diff --git a/helper/schema/field_reader_config_test.go b/helper/schema/field_reader_config_test.go
index be266a57c..d27f74f36 100644
--- a/helper/schema/field_reader_config_test.go
+++ b/helper/schema/field_reader_config_test.go
@@ -184,24 +184,24 @@ func TestConfigFieldReader(t *testing.T) {
 	}
 
 	for name, tc := range cases {
-		out, outOk, outComputed, outErr := r.ReadField(tc.Addr, tc.Schema)
-		if (outErr != nil) != tc.OutErr {
-			t.Fatalf("%s: err: %s", name, outErr)
+		out, err := r.ReadField(tc.Addr, tc.Schema)
+		if (err != nil) != tc.OutErr {
+			t.Fatalf("%s: err: %s", name, err)
 		}
-		if outComputed != tc.OutComputed {
-			t.Fatalf("%s: err: %#v", name, outComputed)
+		if out.Computed != tc.OutComputed {
+			t.Fatalf("%s: err: %#v", name, out.Computed)
 		}
 
-		if s, ok := out.(*Set); ok {
+		if s, ok := out.Value.(*Set); ok {
 			// If it is a set, convert to a list so its more easily checked.
-			out = s.List()
+			out.Value = s.List()
 		}
 
-		if !reflect.DeepEqual(out, tc.Out) {
-			t.Fatalf("%s: out: %#v", name, out)
+		if !reflect.DeepEqual(out.Value, tc.Out) {
+			t.Fatalf("%s: out: %#v", name, out.Value)
 		}
-		if outOk != tc.OutOk {
-			t.Fatalf("%s: outOk: %#v", name, outOk)
+		if out.Exists != tc.OutOk {
+			t.Fatalf("%s: outOk: %#v", name, out.Exists)
 		}
 	}
 }
diff --git a/helper/schema/field_reader_diff.go b/helper/schema/field_reader_diff.go
new file mode 100644
index 000000000..c35380120
--- /dev/null
+++ b/helper/schema/field_reader_diff.go
@@ -0,0 +1,152 @@
+package schema
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/hashicorp/terraform/terraform"
+	"github.com/mitchellh/mapstructure"
+)
+
+// DiffFieldReader reads fields out of a diff structures.
+type DiffFieldReader struct {
+	Diff *terraform.InstanceDiff
+}
+
+func (r *DiffFieldReader) ReadField(
+	address []string, schema *Schema) (FieldReadResult, error) {
+	k := strings.Join(address, ".")
+
+	switch schema.Type {
+	case TypeBool:
+		fallthrough
+	case TypeInt:
+		fallthrough
+	case TypeString:
+		return r.readPrimitive(k, schema)
+	case TypeList:
+		return readListField(r, k, schema)
+	case TypeMap:
+		return r.readMap(k)
+	case TypeSet:
+		return r.readSet(k, schema)
+	case typeObject:
+		return readObjectField(r, k, schema.Elem.(map[string]*Schema))
+	default:
+		panic(fmt.Sprintf("Unknown type: %#v", schema.Type))
+	}
+}
+
+func (r *DiffFieldReader) readMap(k string) (FieldReadResult, error) {
+	result := make(map[string]interface{})
+	negresult := make(map[string]interface{})
+	resultSet := false
+
+	prefix := k + "."
+	for k, v := range r.Diff.Attributes {
+		if !strings.HasPrefix(k, prefix) {
+			continue
+		}
+		resultSet = true
+
+		k = k[len(prefix):]
+		if v.NewRemoved {
+			negresult[k] = ""
+			continue
+		}
+
+		result[k] = v.New
+	}
+
+	var resultVal interface{}
+	if resultSet {
+		resultVal = result
+	}
+
+	return FieldReadResult{
+		Value:    resultVal,
+		NegValue: negresult,
+		Exists:   resultSet,
+	}, nil
+}
+
+func (r *DiffFieldReader) readPrimitive(
+	k string, schema *Schema) (FieldReadResult, error) {
+	attrD, ok := r.Diff.Attributes[k]
+	if !ok {
+		return FieldReadResult{}, nil
+	}
+	if attrD.NewComputed {
+		return FieldReadResult{
+			Exists:   true,
+			Computed: true,
+		}, nil
+	}
+
+	result := attrD.New
+	if attrD.NewExtra != nil {
+		if err := mapstructure.WeakDecode(attrD.NewExtra, &result); err != nil {
+			return FieldReadResult{}, err
+		}
+	}
+
+	returnVal, err := stringToPrimitive(result, false, schema)
+	if err != nil {
+		return FieldReadResult{}, err
+	}
+
+	return FieldReadResult{
+		Value:  returnVal,
+		Exists: true,
+	}, nil
+}
+
+func (r *DiffFieldReader) readSet(
+	k string, schema *Schema) (FieldReadResult, error) {
+	// Create the set that will be our result
+	set := &Set{F: schema.Set}
+
+	// Get the schema for the elements
+	var elemSchema *Schema
+	switch t := schema.Elem.(type) {
+	case *Resource:
+		elemSchema = &Schema{
+			Type: typeObject,
+			Elem: t.Schema,
+		}
+	case *Schema:
+		elemSchema = t
+	}
+
+	// Go through the map and find all the set items
+	prefix := k + "."
+	for k, _ := range r.Diff.Attributes {
+		if !strings.HasPrefix(k, prefix) {
+			continue
+		}
+		if strings.HasPrefix(k, prefix+"#") {
+			// Ignore the count field
+			continue
+		}
+
+		// Split the key, since it might be a sub-object like "idx.field"
+		parts := strings.Split(k[len(prefix):], ".")
+		idx := parts[0]
+
+		raw, err := r.ReadField([]string{prefix + idx}, elemSchema)
+		if err != nil {
+			return FieldReadResult{}, err
+		}
+		if !raw.Exists {
+			// This shouldn't happen because we just verified it does exist
+			panic("missing field in set: " + k + "." + idx)
+		}
+
+		set.Add(raw.Value)
+	}
+
+	return FieldReadResult{
+		Value:  set,
+		Exists: true,
+	}, nil
+}
diff --git a/helper/schema/field_reader_diff_test.go b/helper/schema/field_reader_diff_test.go
new file mode 100644
index 000000000..8cb384d92
--- /dev/null
+++ b/helper/schema/field_reader_diff_test.go
@@ -0,0 +1,313 @@
+package schema
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/hashicorp/terraform/terraform"
+)
+
+func TestDiffFieldReader_impl(t *testing.T) {
+	var _ FieldReader = new(DiffFieldReader)
+}
+
+func TestDiffFieldReader(t *testing.T) {
+	r := &DiffFieldReader{
+		Diff: &terraform.InstanceDiff{
+			Attributes: map[string]*terraform.ResourceAttrDiff{
+				"bool": &terraform.ResourceAttrDiff{
+					Old: "",
+					New: "true",
+				},
+
+				"int": &terraform.ResourceAttrDiff{
+					Old: "",
+					New: "42",
+				},
+
+				"string": &terraform.ResourceAttrDiff{
+					Old: "",
+					New: "string",
+				},
+
+				"list.#": &terraform.ResourceAttrDiff{
+					Old: "0",
+					New: "2",
+				},
+
+				"list.0": &terraform.ResourceAttrDiff{
+					Old: "",
+					New: "foo",
+				},
+
+				"list.1": &terraform.ResourceAttrDiff{
+					Old: "",
+					New: "bar",
+				},
+
+				"listInt.#": &terraform.ResourceAttrDiff{
+					Old: "0",
+					New: "2",
+				},
+
+				"listInt.0": &terraform.ResourceAttrDiff{
+					Old: "",
+					New: "21",
+				},
+
+				"listInt.1": &terraform.ResourceAttrDiff{
+					Old: "",
+					New: "42",
+				},
+
+				"map.foo": &terraform.ResourceAttrDiff{
+					Old: "",
+					New: "bar",
+				},
+
+				"map.bar": &terraform.ResourceAttrDiff{
+					Old: "",
+					New: "baz",
+				},
+
+				"mapRemove.foo": &terraform.ResourceAttrDiff{
+					Old: "",
+					New: "bar",
+				},
+
+				"mapRemove.bar": &terraform.ResourceAttrDiff{
+					NewRemoved: true,
+				},
+
+				"set.#": &terraform.ResourceAttrDiff{
+					Old: "0",
+					New: "2",
+				},
+
+				"set.10": &terraform.ResourceAttrDiff{
+					Old: "",
+					New: "10",
+				},
+
+				"set.50": &terraform.ResourceAttrDiff{
+					Old: "",
+					New: "50",
+				},
+
+				"setDeep.#": &terraform.ResourceAttrDiff{
+					Old: "0",
+					New: "2",
+				},
+
+				"setDeep.10.index": &terraform.ResourceAttrDiff{
+					Old: "",
+					New: "10",
+				},
+
+				"setDeep.10.value": &terraform.ResourceAttrDiff{
+					Old: "",
+					New: "foo",
+				},
+
+				"setDeep.50.index": &terraform.ResourceAttrDiff{
+					Old: "",
+					New: "50",
+				},
+
+				"setDeep.50.value": &terraform.ResourceAttrDiff{
+					Old: "",
+					New: "bar",
+				},
+			},
+		},
+	}
+
+	cases := map[string]struct {
+		Addr   []string
+		Schema *Schema
+		Result FieldReadResult
+		Err    bool
+	}{
+		"noexist": {
+			[]string{"boolNOPE"},
+			&Schema{Type: TypeBool},
+			FieldReadResult{
+				Value:    nil,
+				Exists:   false,
+				Computed: false,
+			},
+			false,
+		},
+
+		"bool": {
+			[]string{"bool"},
+			&Schema{Type: TypeBool},
+			FieldReadResult{
+				Value:    true,
+				Exists:   true,
+				Computed: false,
+			},
+			false,
+		},
+
+		"int": {
+			[]string{"int"},
+			&Schema{Type: TypeInt},
+			FieldReadResult{
+				Value:    42,
+				Exists:   true,
+				Computed: false,
+			},
+			false,
+		},
+
+		"string": {
+			[]string{"string"},
+			&Schema{Type: TypeString},
+			FieldReadResult{
+				Value:    "string",
+				Exists:   true,
+				Computed: false,
+			},
+			false,
+		},
+
+		"list": {
+			[]string{"list"},
+			&Schema{
+				Type: TypeList,
+				Elem: &Schema{Type: TypeString},
+			},
+			FieldReadResult{
+				Value: []interface{}{
+					"foo",
+					"bar",
+				},
+				Exists:   true,
+				Computed: false,
+			},
+			false,
+		},
+
+		"listInt": {
+			[]string{"listInt"},
+			&Schema{
+				Type: TypeList,
+				Elem: &Schema{Type: TypeInt},
+			},
+			FieldReadResult{
+				Value: []interface{}{
+					21,
+					42,
+				},
+				Exists:   true,
+				Computed: false,
+			},
+			false,
+		},
+
+		"map": {
+			[]string{"map"},
+			&Schema{Type: TypeMap},
+			FieldReadResult{
+				Value: map[string]interface{}{
+					"foo": "bar",
+					"bar": "baz",
+				},
+				NegValue: map[string]interface{}{},
+				Exists:   true,
+				Computed: false,
+			},
+			false,
+		},
+
+		"mapelem": {
+			[]string{"map", "foo"},
+			&Schema{Type: TypeString},
+			FieldReadResult{
+				Value:    "bar",
+				Exists:   true,
+				Computed: false,
+			},
+			false,
+		},
+
+		"mapRemove": {
+			[]string{"mapRemove"},
+			&Schema{Type: TypeMap},
+			FieldReadResult{
+				Value: map[string]interface{}{
+					"foo": "bar",
+				},
+				NegValue: map[string]interface{}{
+					"bar": "",
+				},
+				Exists:   true,
+				Computed: false,
+			},
+			false,
+		},
+
+		"set": {
+			[]string{"set"},
+			&Schema{
+				Type: TypeSet,
+				Elem: &Schema{Type: TypeInt},
+				Set: func(a interface{}) int {
+					return a.(int)
+				},
+			},
+			FieldReadResult{
+				Value:    []interface{}{10, 50},
+				Exists:   true,
+				Computed: false,
+			},
+			false,
+		},
+
+		"setDeep": {
+			[]string{"setDeep"},
+			&Schema{
+				Type: TypeSet,
+				Elem: &Resource{
+					Schema: map[string]*Schema{
+						"index": &Schema{Type: TypeInt},
+						"value": &Schema{Type: TypeString},
+					},
+				},
+				Set: func(a interface{}) int {
+					return a.(map[string]interface{})["index"].(int)
+				},
+			},
+			FieldReadResult{
+				Value: []interface{}{
+					map[string]interface{}{
+						"index": 10,
+						"value": "foo",
+					},
+					map[string]interface{}{
+						"index": 50,
+						"value": "bar",
+					},
+				},
+				Exists:   true,
+				Computed: false,
+			},
+			false,
+		},
+	}
+
+	for name, tc := range cases {
+		out, err := r.ReadField(tc.Addr, tc.Schema)
+		if (err != nil) != tc.Err {
+			t.Fatalf("%s: err: %s", name, err)
+		}
+		if s, ok := out.Value.(*Set); ok {
+			// If it is a set, convert to a list so its more easily checked.
+			out.Value = s.List()
+		}
+		if !reflect.DeepEqual(tc.Result, out) {
+			t.Fatalf("%s: bad: %#v", name, out)
+		}
+	}
+}
diff --git a/helper/schema/field_reader_map.go b/helper/schema/field_reader_map.go
index 190219c6a..8eafdd13f 100644
--- a/helper/schema/field_reader_map.go
+++ b/helper/schema/field_reader_map.go
@@ -12,7 +12,7 @@ type MapFieldReader struct {
 }
 
 func (r *MapFieldReader) ReadField(
-	address []string, schema *Schema) (interface{}, bool, bool, error) {
+	address []string, schema *Schema) (FieldReadResult, error) {
 	k := strings.Join(address, ".")
 
 	switch schema.Type {
@@ -35,7 +35,7 @@ func (r *MapFieldReader) ReadField(
 	}
 }
 
-func (r *MapFieldReader) readMap(k string) (interface{}, bool, bool, error) {
+func (r *MapFieldReader) readMap(k string) (FieldReadResult, error) {
 	result := make(map[string]interface{})
 	resultSet := false
 
@@ -54,43 +54,52 @@ func (r *MapFieldReader) readMap(k string) (interface{}, bool, bool, error) {
 		resultVal = result
 	}
 
-	return resultVal, resultSet, false, nil
+	return FieldReadResult{
+		Value:  resultVal,
+		Exists: resultSet,
+	}, nil
 }
 
 func (r *MapFieldReader) readPrimitive(
-	k string, schema *Schema) (interface{}, bool, bool, error) {
+	k string, schema *Schema) (FieldReadResult, error) {
 	result, ok := r.Map[k]
 	if !ok {
-		return nil, false, false, nil
+		return FieldReadResult{}, nil
 	}
 
 	returnVal, err := stringToPrimitive(result, false, schema)
 	if err != nil {
-		return nil, false, false, err
+		return FieldReadResult{}, err
 	}
 
-	return returnVal, true, false, nil
+	return FieldReadResult{
+		Value:  returnVal,
+		Exists: true,
+	}, nil
 }
 
 func (r *MapFieldReader) readSet(
-	k string, schema *Schema) (interface{}, bool, bool, error) {
+	k string, schema *Schema) (FieldReadResult, error) {
 	// Get the number of elements in the list
-	countRaw, countOk, countComputed, err := r.readPrimitive(
-		k+".#", &Schema{Type: TypeInt})
+	countRaw, err := r.readPrimitive(k+".#", &Schema{Type: TypeInt})
 	if err != nil {
-		return nil, false, false, err
+		return FieldReadResult{}, err
 	}
-	if !countOk {
+	if !countRaw.Exists {
 		// No count, means we have no list
-		countRaw = 0
+		countRaw.Value = 0
 	}
 
 	// Create the set that will be our result
 	set := &Set{F: schema.Set}
 
 	// If we have an empty list, then return an empty list
-	if countComputed || countRaw.(int) == 0 {
-		return set, true, countComputed, nil
+	if countRaw.Computed || countRaw.Value.(int) == 0 {
+		return FieldReadResult{
+			Value:    set,
+			Exists:   true,
+			Computed: countRaw.Computed,
+		}, nil
 	}
 
 	// Get the schema for the elements
@@ -120,17 +129,20 @@ func (r *MapFieldReader) readSet(
 		parts := strings.Split(k[len(prefix):], ".")
 		idx := parts[0]
 
-		v, ok, _, err := r.ReadField([]string{prefix + idx}, elemSchema)
+		raw, err := r.ReadField([]string{prefix + idx}, elemSchema)
 		if err != nil {
-			return nil, false, false, err
+			return FieldReadResult{}, err
 		}
-		if !ok {
+		if !raw.Exists {
 			// This shouldn't happen because we just verified it does exist
 			panic("missing field in set: " + k + "." + idx)
 		}
 
-		set.Add(v)
+		set.Add(raw.Value)
 	}
 
-	return set, true, false, nil
+	return FieldReadResult{
+		Value:  set,
+		Exists: true,
+	}, nil
 }
diff --git a/helper/schema/field_reader_map_test.go b/helper/schema/field_reader_map_test.go
index fba89a158..4334c0a5a 100644
--- a/helper/schema/field_reader_map_test.go
+++ b/helper/schema/field_reader_map_test.go
@@ -180,24 +180,24 @@ func TestMapFieldReader(t *testing.T) {
 	}
 
 	for name, tc := range cases {
-		out, outOk, outComputed, outErr := r.ReadField(tc.Addr, tc.Schema)
-		if (outErr != nil) != tc.OutErr {
-			t.Fatalf("%s: err: %s", name, outErr)
+		out, err := r.ReadField(tc.Addr, tc.Schema)
+		if (err != nil) != tc.OutErr {
+			t.Fatalf("%s: err: %s", name, err)
 		}
-		if outComputed != tc.OutComputed {
-			t.Fatalf("%s: err: %#v", name, outComputed)
+		if out.Computed != tc.OutComputed {
+			t.Fatalf("%s: err: %#v", name, out.Computed)
 		}
 
-		if s, ok := out.(*Set); ok {
+		if s, ok := out.Value.(*Set); ok {
 			// If it is a set, convert to a list so its more easily checked.
-			out = s.List()
+			out.Value = s.List()
 		}
 
-		if !reflect.DeepEqual(out, tc.Out) {
-			t.Fatalf("%s: out: %#v", name, out)
+		if !reflect.DeepEqual(out.Value, tc.Out) {
+			t.Fatalf("%s: out: %#v", name, out.Value)
 		}
-		if outOk != tc.OutOk {
-			t.Fatalf("%s: outOk: %#v", name, outOk)
+		if out.Exists != tc.OutOk {
+			t.Fatalf("%s: outOk: %#v", name, out.Exists)
 		}
 	}
 }