diff --git a/message.go b/message.go
index 42e00aa..2e2ce7c 100644
--- a/message.go
+++ b/message.go
@@ -200,7 +200,7 @@ func (m *Message) DelHeader(field string) {
 // SetBody sets the body of the message.
 func (m *Message) SetBody(contentType, body string) {
 	m.parts = []part{
-		part{
+		{
 			contentType: contentType,
 			copier: func(w io.Writer) error {
 				_, err := io.WriteString(w, body)
@@ -243,7 +243,7 @@ func (m *Message) AddAlternative(contentType, body string) {
 //	})
 func (m *Message) AddAlternativeWriter(contentType string, f func(io.Writer) error) {
 	m.parts = []part{
-		part{
+		{
 			contentType: contentType,
 			copier:      f,
 		},
diff --git a/writeto.go b/writeto.go
index efe4123..cdc10a0 100644
--- a/writeto.go
+++ b/writeto.go
@@ -40,8 +40,8 @@ func (w *messageWriter) writeMessage(m *Message) {
 	for _, part := range m.parts {
 		contentType := part.contentType + "; charset=" + m.charset
 		w.writeHeaders(map[string][]string{
-			"Content-Type":              []string{contentType},
-			"Content-Transfer-Encoding": []string{string(m.encoding)},
+			"Content-Type":              {contentType},
+			"Content-Transfer-Encoding": {string(m.encoding)},
 		})
 		w.writeBody(part.copier, m.encoding)
 	}
@@ -91,7 +91,7 @@ func (w *messageWriter) openMultipart(mimeType string) {
 		w.writeString("\r\n")
 	} else {
 		w.createPart(map[string][]string{
-			"Content-Type": []string{contentType},
+			"Content-Type": {contentType},
 		})
 	}
 	w.depth++