diff --git a/binding/form_mapping.go b/binding/form_mapping.go
index cb66dd4a..743ee19d 100644
--- a/binding/form_mapping.go
+++ b/binding/form_mapping.go
@@ -17,7 +17,8 @@ import (
 )
 
 var (
-	errUnknownType = errors.New("unknown type")
+	// ErrUnknownType unknown type
+	ErrUnknownType = errors.New("unknown type")
 
 	// ErrConvertMapStringSlice can not covert to map[string][]string
 	ErrConvertMapStringSlice = errors.New("can not convert to map slices of strings")
@@ -164,7 +165,7 @@ func tryToSetValue(value reflect.Value, field reflect.StructField, setter setter
 	return setter.TrySet(value, field, tagValue, setOpt)
 }
 
-func setByForm(value reflect.Value, field reflect.StructField, form map[string][]string, tagValue string, opt setOptions) (isSetted bool, err error) {
+func setByForm(value reflect.Value, field reflect.StructField, form map[string][]string, tagValue string, opt setOptions) (bool, error) {
 	vs, ok := form[tagValue]
 	if !ok && !opt.isDefaultExists {
 		return false, nil
@@ -240,7 +241,7 @@ func setWithProperType(val string, value reflect.Value, field reflect.StructFiel
 	case reflect.Map:
 		return json.Unmarshal(bytesconv.StringToBytes(val), value.Addr().Interface())
 	default:
-		return errUnknownType
+		return ErrUnknownType
 	}
 	return nil
 }
diff --git a/binding/form_mapping_test.go b/binding/form_mapping_test.go
index 608594e2..51f6d19c 100644
--- a/binding/form_mapping_test.go
+++ b/binding/form_mapping_test.go
@@ -124,7 +124,7 @@ func TestMappingUnknownFieldType(t *testing.T) {
 
 	err := mappingByPtr(&s, formSource{"U": {"unknown"}}, "form")
 	assert.Error(t, err)
-	assert.Equal(t, errUnknownType, err)
+	assert.Equal(t, ErrUnknownType, err)
 }
 
 func TestMappingURI(t *testing.T) {
diff --git a/binding/multipart_form_mapping.go b/binding/multipart_form_mapping.go
index 69c0a544..b8887105 100644
--- a/binding/multipart_form_mapping.go
+++ b/binding/multipart_form_mapping.go
@@ -32,7 +32,7 @@ func (r *multipartRequest) TrySet(value reflect.Value, field reflect.StructField
 	return setByForm(value, field, r.MultipartForm.Value, key, opt)
 }
 
-func setByMultipartFormFile(value reflect.Value, field reflect.StructField, files []*multipart.FileHeader) (isSetted bool, err error) {
+func setByMultipartFormFile(value reflect.Value, field reflect.StructField, files []*multipart.FileHeader) (bool, error) {
 	switch value.Kind() {
 	case reflect.Ptr:
 		switch value.Interface().(type) {
@@ -48,7 +48,7 @@ func setByMultipartFormFile(value reflect.Value, field reflect.StructField, file
 		}
 	case reflect.Slice:
 		slice := reflect.MakeSlice(value.Type(), len(files), len(files))
-		isSetted, err = setArrayOfMultipartFormFiles(slice, field, files)
+		isSetted, err := setArrayOfMultipartFormFiles(slice, field, files)
 		if err != nil || !isSetted {
 			return isSetted, err
 		}
@@ -60,7 +60,7 @@ func setByMultipartFormFile(value reflect.Value, field reflect.StructField, file
 	return false, ErrMultiFileHeader
 }
 
-func setArrayOfMultipartFormFiles(value reflect.Value, field reflect.StructField, files []*multipart.FileHeader) (isSetted bool, err error) {
+func setArrayOfMultipartFormFiles(value reflect.Value, field reflect.StructField, files []*multipart.FileHeader) (bool, error) {
 	if value.Len() != len(files) {
 		return false, ErrMultiFileHeaderLenInvalid
 	}