diff --git a/README.md b/README.md
index 7dd63152..b52d5777 100644
--- a/README.md
+++ b/README.md
@@ -26,7 +26,7 @@ import "github.com/nicksnyder/go-i18n/v2/i18n"
 Create a Bundle to use for the lifetime of your application.
 
 ```go
-bundle := i18n.NewBundle(language.English)
+bundle := &i18n.Bundle{DefaultLanguage: language.English}
 ```
 
 Create a Localizer to use for a set of language preferences.
diff --git a/v2/example/main.go b/v2/example/main.go
index 838e1456..e10ff80f 100644
--- a/v2/example/main.go
+++ b/v2/example/main.go
@@ -27,7 +27,7 @@ var page = template.Must(template.New("").Parse(`
 `))
 
 func main() {
-	bundle := i18n.NewBundle(language.English)
+	bundle := &i18n.Bundle{DefaultLanguage: language.English}
 	bundle.RegisterUnmarshalFunc("toml", toml.Unmarshal)
 	// No need to load active.en.toml since we are providing default translations.
 	// bundle.MustLoadMessageFile("active.en.toml")
diff --git a/v2/goi18n/extract_command_test.go b/v2/goi18n/extract_command_test.go
index 38184301..0347041e 100644
--- a/v2/goi18n/extract_command_test.go
+++ b/v2/goi18n/extract_command_test.go
@@ -50,7 +50,7 @@ func TestExtract(t *testing.T) {
 			import "github.com/nicksnyder/go-i18n/v2/i18n"
 
 			func main() {
-				bundle := i18n.NewBundle()
+				bundle := &i18n.Bundle{}
 				l := i18n.NewLocalizer(bundle, "en")
 				l.Localize(&i18n.LocalizeConfig{MessageID: "Plural ID"})
 			}
@@ -69,7 +69,7 @@ func TestExtract(t *testing.T) {
 			import "github.com/nicksnyder/go-i18n/v2/i18n"
 
 			func main() {
-				bundle := i18n.NewBundle()
+				bundle := &i18n.Bundle{}
 				l := i18n.NewLocalizer(bundle, "en")
 				l.MustLocalize(&i18n.LocalizeConfig{MessageID: "Plural ID"})
 			}
diff --git a/v2/i18n/bundle.go b/v2/i18n/bundle.go
index 4bb89e1c..2a8faaf2 100644
--- a/v2/i18n/bundle.go
+++ b/v2/i18n/bundle.go
@@ -1,7 +1,6 @@
 package i18n
 
 import (
-	"encoding/json"
 	"fmt"
 	"io/ioutil"
 
@@ -18,34 +17,31 @@ type UnmarshalFunc = internal.UnmarshalFunc
 // Most applications only need a single bundle
 // that is initialized early in the application's lifecycle.
 type Bundle struct {
+	// DefaultLanguage is the default language of the bundle.
+	DefaultLanguage language.Tag
+
+	// UnmarshalFuncs is a map of file extensions to UnmarshalFuncs.
+	UnmarshalFuncs map[string]UnmarshalFunc
+
 	messageTemplates map[language.Tag]map[string]*internal.MessageTemplate
 	pluralRules      plural.Rules
-	unmarshalFuncs   map[string]UnmarshalFunc
-	defaultTag       language.Tag
 	tags             []language.Tag
 	matcher          language.Matcher
 }
 
-// NewBundle returns a new bundle that contains the
-// CLDR plural rules and a json unmarshaler.
-func NewBundle(defaultTag language.Tag) *Bundle {
-	b := &Bundle{
-		defaultTag:  defaultTag,
-		pluralRules: plural.DefaultRules(),
-		unmarshalFuncs: map[string]UnmarshalFunc{
-			"json": json.Unmarshal,
-		},
+func (b *Bundle) init() {
+	if b.pluralRules == nil {
+		b.pluralRules = plural.DefaultRules()
 	}
-	b.addTag(defaultTag)
-	return b
+	b.addTag(b.DefaultLanguage)
 }
 
 // RegisterUnmarshalFunc registers an UnmarshalFunc for format.
 func (b *Bundle) RegisterUnmarshalFunc(format string, unmarshalFunc UnmarshalFunc) {
-	if b.unmarshalFuncs == nil {
-		b.unmarshalFuncs = make(map[string]UnmarshalFunc)
+	if b.UnmarshalFuncs == nil {
+		b.UnmarshalFuncs = make(map[string]UnmarshalFunc)
 	}
-	b.unmarshalFuncs[format] = unmarshalFunc
+	b.UnmarshalFuncs[format] = unmarshalFunc
 }
 
 // LoadMessageFile loads the bytes from path
@@ -75,7 +71,7 @@ type MessageFile = internal.MessageFile
 //
 // The language tag of the file is everything after the second to last "." or after the last path separator, but before the format.
 func (b *Bundle) ParseMessageFileBytes(buf []byte, path string) (*MessageFile, error) {
-	messageFile, err := internal.ParseMessageFileBytes(buf, path, b.unmarshalFuncs)
+	messageFile, err := internal.ParseMessageFileBytes(buf, path, b.UnmarshalFuncs)
 	if err != nil {
 		return nil, err
 	}
@@ -96,9 +92,7 @@ func (b *Bundle) MustParseMessageFileBytes(buf []byte, path string) {
 // AddMessages adds messages for a language.
 // It is useful if your messages are in a format not supported by ParseMessageFileBytes.
 func (b *Bundle) AddMessages(tag language.Tag, messages ...*Message) error {
-	if b.pluralRules == nil {
-		b.pluralRules = plural.DefaultRules()
-	}
+	b.init()
 	pluralRule := b.pluralRules.Rule(tag)
 	if pluralRule == nil {
 		return fmt.Errorf("no plural rule registered for %s", tag)
diff --git a/v2/i18n/bundle_test.go b/v2/i18n/bundle_test.go
index 037a17c5..43f40202 100644
--- a/v2/i18n/bundle_test.go
+++ b/v2/i18n/bundle_test.go
@@ -1,7 +1,6 @@
 package i18n
 
 import (
-	"encoding/json"
 	"reflect"
 	"testing"
 
@@ -34,7 +33,7 @@ var everythingMessage = internal.MustNewMessage(map[string]string{
 })
 
 func TestPseudoLanguage(t *testing.T) {
-	bundle := NewBundle(language.English)
+	bundle := &Bundle{DefaultLanguage: language.English}
 	bundle.RegisterUnmarshalFunc("toml", toml.Unmarshal)
 	expected := "simple simple"
 	bundle.MustParseMessageFileBytes([]byte(`
@@ -52,7 +51,7 @@ simple = "simple simple"
 }
 
 func TestPseudoLanguagePlural(t *testing.T) {
-	bundle := NewBundle(language.English)
+	bundle := &Bundle{DefaultLanguage: language.English}
 	bundle.RegisterUnmarshalFunc("toml", toml.Unmarshal)
 	bundle.MustParseMessageFileBytes([]byte(`
 [everything]
@@ -82,7 +81,6 @@ zero = "zero translation"
 
 func TestJSON(t *testing.T) {
 	var bundle Bundle
-	bundle.RegisterUnmarshalFunc("json", json.Unmarshal)
 	bundle.MustParseMessageFileBytes([]byte(`{
 	"simple": "simple translation",
 	"detail": {
@@ -163,7 +161,6 @@ other = "other translation"
 
 func TestV1Format(t *testing.T) {
 	var bundle Bundle
-	bundle.RegisterUnmarshalFunc("json", json.Unmarshal)
 	bundle.MustParseMessageFileBytes([]byte(`[
 	{
 		"id": "simple",
@@ -191,7 +188,6 @@ func TestV1Format(t *testing.T) {
 
 func TestV1FlatFormat(t *testing.T) {
 	var bundle Bundle
-	bundle.RegisterUnmarshalFunc("json", json.Unmarshal)
 	bundle.MustParseMessageFileBytes([]byte(`{
 	"simple": {
 		"other": "simple translation"
diff --git a/v2/i18n/doc.go b/v2/i18n/doc.go
index 5b79a113..7b56a717 100644
--- a/v2/i18n/doc.go
+++ b/v2/i18n/doc.go
@@ -2,7 +2,7 @@
 // according to a set of locale preferences.
 //
 // Create a Bundle to use for the lifetime of your application.
-//     bundle := i18n.NewBundle(language.English)
+//     bundle := &i18n.Bundle{DefaultLanguage: language.English}
 //
 // Create a Localizer to use for a set of language preferences.
 //     func(w http.ResponseWriter, r *http.Request) {
diff --git a/v2/i18n/example_test.go b/v2/i18n/example_test.go
index 2256e636..13fd6413 100644
--- a/v2/i18n/example_test.go
+++ b/v2/i18n/example_test.go
@@ -9,7 +9,7 @@ import (
 )
 
 func ExampleLocalizer_MustLocalize() {
-	bundle := i18n.NewBundle(language.English)
+	bundle := &i18n.Bundle{DefaultLanguage: language.English}
 	localizer := i18n.NewLocalizer(bundle, "en")
 	fmt.Println(localizer.MustLocalize(&i18n.LocalizeConfig{
 		DefaultMessage: &i18n.Message{
@@ -22,7 +22,7 @@ func ExampleLocalizer_MustLocalize() {
 }
 
 func ExampleLocalizer_MustLocalize_noDefaultMessage() {
-	bundle := i18n.NewBundle(language.English)
+	bundle := &i18n.Bundle{DefaultLanguage: language.English}
 	bundle.RegisterUnmarshalFunc("toml", toml.Unmarshal)
 	bundle.MustParseMessageFileBytes([]byte(`
 HelloWorld = "Hello World!"
@@ -45,7 +45,7 @@ HelloWorld = "Hola Mundo!"
 }
 
 func ExampleLocalizer_MustLocalize_plural() {
-	bundle := i18n.NewBundle(language.English)
+	bundle := &i18n.Bundle{DefaultLanguage: language.English}
 	localizer := i18n.NewLocalizer(bundle, "en")
 	catsMessage := &i18n.Message{
 		ID:    "Cats",
@@ -71,7 +71,7 @@ func ExampleLocalizer_MustLocalize_plural() {
 }
 
 func ExampleLocalizer_MustLocalize_template() {
-	bundle := i18n.NewBundle(language.English)
+	bundle := &i18n.Bundle{DefaultLanguage: language.English}
 	localizer := i18n.NewLocalizer(bundle, "en")
 	helloPersonMessage := &i18n.Message{
 		ID:    "HelloPerson",
@@ -86,7 +86,7 @@ func ExampleLocalizer_MustLocalize_template() {
 }
 
 func ExampleLocalizer_MustLocalize_plural_template() {
-	bundle := i18n.NewBundle(language.English)
+	bundle := &i18n.Bundle{DefaultLanguage: language.English}
 	localizer := i18n.NewLocalizer(bundle, "en")
 	personCatsMessage := &i18n.Message{
 		ID:    "PersonCats",
@@ -124,7 +124,7 @@ func ExampleLocalizer_MustLocalize_plural_template() {
 }
 
 func ExampleLocalizer_MustLocalize_customTemplateDelims() {
-	bundle := i18n.NewBundle(language.English)
+	bundle := &i18n.Bundle{DefaultLanguage: language.English}
 	localizer := i18n.NewLocalizer(bundle, "en")
 	helloPersonMessage := &i18n.Message{
 		ID:         "HelloPerson",
diff --git a/v2/i18n/localizer.go b/v2/i18n/localizer.go
index 1e5dc00d..f9d516fa 100644
--- a/v2/i18n/localizer.go
+++ b/v2/i18n/localizer.go
@@ -24,6 +24,7 @@ type Localizer struct {
 // in the bundle according to the language preferences in langs.
 // It can parse Accept-Language headers as defined in http://www.ietf.org/rfc/rfc2616.txt.
 func NewLocalizer(bundle *Bundle, langs ...string) *Localizer {
+	bundle.init()
 	return &Localizer{
 		bundle: bundle,
 		tags:   parseTags(langs),
@@ -129,7 +130,7 @@ func (l *Localizer) getTemplate(id string, defaultMessage *Message) (language.Ta
 	if template != nil {
 		return fastTag, template
 	}
-	if fastTag == l.bundle.defaultTag {
+	if fastTag == l.bundle.DefaultLanguage {
 		if defaultMessage == nil {
 			return fastTag, nil
 		}
@@ -141,8 +142,8 @@ func (l *Localizer) getTemplate(id string, defaultMessage *Message) (language.Ta
 		// so we need to create a new matcher that contains only the tags in the bundle
 		// that have this message.
 		foundTags := make([]language.Tag, 0, len(l.bundle.messageTemplates))
-		if l.bundle.defaultTag != fastTag {
-			foundTags = append(foundTags, l.bundle.defaultTag)
+		if l.bundle.DefaultLanguage != fastTag {
+			foundTags = append(foundTags, l.bundle.DefaultLanguage)
 		}
 		for t, templates := range l.bundle.messageTemplates {
 			if t == fastTag {
@@ -161,9 +162,9 @@ func (l *Localizer) getTemplate(id string, defaultMessage *Message) (language.Ta
 		}
 	}
 	if defaultMessage == nil {
-		return l.bundle.defaultTag, nil
+		return l.bundle.DefaultLanguage, nil
 	}
-	return l.bundle.defaultTag, internal.NewMessageTemplate(defaultMessage)
+	return l.bundle.DefaultLanguage, internal.NewMessageTemplate(defaultMessage)
 }
 
 func (l *Localizer) matchTemplate(id string, matcher language.Matcher, tags []language.Tag) (language.Tag, *internal.MessageTemplate) {
diff --git a/v2/i18n/localizer_test.go b/v2/i18n/localizer_test.go
index be15afd5..9df62f58 100644
--- a/v2/i18n/localizer_test.go
+++ b/v2/i18n/localizer_test.go
@@ -476,7 +476,7 @@ func TestLocalizer_Localize(t *testing.T) {
 	}
 	for _, testCase := range testCases {
 		t.Run(testCase.name, func(t *testing.T) {
-			bundle := NewBundle(testCase.defaultLanguage)
+			bundle := &Bundle{DefaultLanguage: testCase.defaultLanguage}
 			for tag, messages := range testCase.messages {
 				bundle.AddMessages(tag, messages...)
 			}
diff --git a/v2/internal/parse.go b/v2/internal/parse.go
index 171a1e30..a5cee87c 100644
--- a/v2/internal/parse.go
+++ b/v2/internal/parse.go
@@ -1,6 +1,7 @@
 package internal
 
 import (
+	"encoding/json"
 	"fmt"
 	"os"
 
@@ -30,12 +31,13 @@ func ParseMessageFileBytes(buf []byte, path string, unmarshalFuncs map[string]Un
 	if len(buf) == 0 {
 		return messageFile, nil
 	}
-	var unmarshalFunc UnmarshalFunc
-	if unmarshalFuncs != nil {
-		unmarshalFunc = unmarshalFuncs[messageFile.Format]
-	}
+	unmarshalFunc := unmarshalFuncs[messageFile.Format]
 	if unmarshalFunc == nil {
-		return nil, fmt.Errorf("no unmarshaler registered for %s", messageFile.Format)
+		if messageFile.Format == "json" {
+			unmarshalFunc = json.Unmarshal
+		} else {
+			return nil, fmt.Errorf("no unmarshaler registered for %s", messageFile.Format)
+		}
 	}
 	var raw interface{}
 	if err := unmarshalFunc(buf, &raw); err != nil {
diff --git a/v2/internal/parse_test.go b/v2/internal/parse_test.go
new file mode 100644
index 00000000..dfe65a3b
--- /dev/null
+++ b/v2/internal/parse_test.go
@@ -0,0 +1,50 @@
+package internal
+
+import (
+	"reflect"
+	"testing"
+
+	"golang.org/x/text/language"
+)
+
+func TestParseMessageFileBytes(t *testing.T) {
+	testCases := []struct {
+		file           string
+		path           string
+		unmarshalFuncs map[string]UnmarshalFunc
+		messageFile    *MessageFile
+		err            error
+	}{
+		{
+			file: `{"hello": "world"}`,
+			path: "en.json",
+			messageFile: &MessageFile{
+				Path:   "en.json",
+				Tag:    language.English,
+				Format: "json",
+				Messages: []*Message{{
+					ID:    "hello",
+					Other: "world",
+				}},
+			},
+		},
+	}
+	for _, testCase := range testCases {
+		actual, err := ParseMessageFileBytes([]byte(testCase.file), testCase.path, testCase.unmarshalFuncs)
+		if err != testCase.err {
+			t.Fatalf("expected error %#v; got %#v", testCase.err, err)
+		}
+		if actual.Path != testCase.messageFile.Path {
+			t.Fatalf("expected path %q; got %q", testCase.messageFile.Path, actual.Path)
+		}
+		if actual.Tag != testCase.messageFile.Tag {
+			t.Fatalf("expected tag %q; got %q", testCase.messageFile.Tag, actual.Tag)
+		}
+		if actual.Format != testCase.messageFile.Format {
+			t.Fatalf("expected format %q; got %q", testCase.messageFile.Format, actual.Format)
+		}
+		if !reflect.DeepEqual(actual.Messages, testCase.messageFile.Messages) {
+			t.Fatalf("expected %#v; got %#v", testCase.messageFile.Messages, actual.Messages)
+		}
+	}
+}