diff --git a/lib/http/response_type.go b/lib/http/response_type.go
index 75fb7146..4fee2e88 100644
--- a/lib/http/response_type.go
+++ b/lib/http/response_type.go
@@ -4,17 +4,17 @@
 
 package http
 
-// ResponseType define type for HTTP response.
-type ResponseType int
+// ResponseType define the content type for HTTP response.
+type ResponseType string
 
 // List of valid response type.
 const (
-	ResponseTypeNone ResponseType = iota
-	ResponseTypeBinary
-	ResponseTypeHTML
-	ResponseTypeJSON
-	ResponseTypePlain
-	ResponseTypeXML
+	ResponseTypeNone   ResponseType = ``
+	ResponseTypeBinary ResponseType = `binary`
+	ResponseTypeHTML   ResponseType = `html`
+	ResponseTypeJSON   ResponseType = `json`
+	ResponseTypePlain  ResponseType = `plain`
+	ResponseTypeXML    ResponseType = `xml`
 )
 
 // String return the string representation of ResponseType as in
diff --git a/lib/http/response_type_test.go b/lib/http/response_type_test.go
index f95726c2..efbc2114 100644
--- a/lib/http/response_type_test.go
+++ b/lib/http/response_type_test.go
@@ -15,12 +15,12 @@ func TestResponseType_String(t *testing.T) {
 		exp     string
 		restype ResponseType
 	}{
-		{restype: 0, exp: ""},
-		{restype: 1, exp: ContentTypeBinary},
-		{restype: 2, exp: ContentTypeHTML},
-		{restype: 3, exp: ContentTypeJSON},
-		{restype: 4, exp: ContentTypePlain},
-		{restype: 5, exp: ContentTypeXML},
+		{restype: ``, exp: ``},
+		{restype: `binary`, exp: ContentTypeBinary},
+		{restype: `html`, exp: ContentTypeHTML},
+		{restype: `json`, exp: ContentTypeJSON},
+		{restype: `plain`, exp: ContentTypePlain},
+		{restype: `xml`, exp: ContentTypeXML},
 		{restype: ResponseTypeNone, exp: ""},
 		{restype: ResponseTypeBinary, exp: ContentTypeBinary},
 		{restype: ResponseTypeHTML, exp: ContentTypeHTML},