diff --git a/bot_test.go b/bot_test.go
index 18cbfdf..0b8d98d 100644
--- a/bot_test.go
+++ b/bot_test.go
@@ -215,13 +215,13 @@ func (s *BotTestSuite) TestSetWebhook() {
 	params := url.Values{
 		"url":             {"hookurl"},
 		"max_connections": {"9"},
-		"allowed_updates": {"message"},
+		"allowed_updates": {"message", "callback_query"},
 	}
 	data := "92839727433"
 	options := &SetWebhookOptions{
 		Certificate:    []byte(data),
 		MaxConnections: 9,
-		AllowedUpdates: []string{"message"},
+		AllowedUpdates: []string{"message", "callback_query"},
 	}
 
 	file := mhttp.File{
@@ -236,6 +236,13 @@ func (s *BotTestSuite) TestSetWebhook() {
 	s.Nil(err)
 }
 
+func (s *BotTestSuite) TestDeleteWebhook() {
+	s.registerRequestCheck("deleteWebhook", "")
+
+	err := s.bot.DeleteWebhook()
+	s.Nil(err)
+}
+
 func (s *BotTestSuite) TestGetChatAdministrators() {
 	s.registerResponse("getChatAdministrators", url.Values{"chat_id": {"123"}}, `{
 		"ok": true,
diff --git a/helpers_test.go b/helpers_test.go
new file mode 100644
index 0000000..23141e0
--- /dev/null
+++ b/helpers_test.go
@@ -0,0 +1,22 @@
+package micha
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type testStruct struct{}
+
+func (s testStruct) MarshalJSON() ([]byte, error) {
+	return nil, errors.New("Some error")
+}
+
+func TestStructToValues(t *testing.T) {
+	_, err := structToValues(testStruct{})
+	assert.NotNil(t, err)
+
+	_, err = structToValues([]string{"1"})
+	assert.NotNil(t, err)
+}
diff --git a/http/http.go b/http/http.go
index 131ccc4..a2a67a2 100644
--- a/http/http.go
+++ b/http/http.go
@@ -37,8 +37,10 @@ func Get(url string) ([]byte, error) {
 
 func Post(url string, data interface{}) ([]byte, error) {
 	body := new(bytes.Buffer)
-	if err := json.NewEncoder(body).Encode(data); err != nil {
-		return nil, fmt.Errorf("Encode data error (%s)", err.Error())
+	if data != nil {
+		if err := json.NewEncoder(body).Encode(data); err != nil {
+			return nil, fmt.Errorf("Encode data error (%s)", err.Error())
+		}
 	}
 
 	request, err := http.NewRequest("POST", url, body)
@@ -72,8 +74,8 @@ func PostMultipart(url string, file *File, params url.Values) ([]byte, error) {
 	}
 
 	for field, values := range params {
-		if len(values) > 0 {
-			if err := writer.WriteField(field, values[0]); err != nil {
+		for i := range values {
+			if err := writer.WriteField(field, values[i]); err != nil {
 				return nil, err
 			}
 		}