diff --git a/cvte.go b/cvte.go
index 198b526..c654272 100644
--- a/cvte.go
+++ b/cvte.go
@@ -57,11 +57,11 @@ func deepStructValues(rv reflect.Value) (sl []interface{}) {
 func deepStructFields(rt reflect.Type) (sl []string) {
 	rt = ptrType(rt)
 
-	type fff struct {
+	type field struct {
 		level int8
 		index int
 	}
-	var exists = make(map[string]fff)
+	var exists = make(map[string]field)
 
 	fn := func(v string, level int8) {
 		ff, ok := exists[v]
@@ -71,7 +71,7 @@ func deepStructFields(rt reflect.Type) (sl []string) {
 			sl = append(sl[:ff.index], sl[ff.index+1:]...)
 		}
 		sl = append(sl, v)
-		exists[v] = fff{level, len(sl) - 1}
+		exists[v] = field{level, len(sl) - 1}
 	}
 
 	// sort by field definition order, include embed field
diff --git a/slice_test.go b/slice_test.go
index 24af2fe..b7c78be 100644
--- a/slice_test.go
+++ b/slice_test.go
@@ -369,9 +369,10 @@ func TestKeysE(t *testing.T) {
 		isErr  bool
 	}{
 		// map
-		{map[int]map[string]interface{}{1: {"1": 111, "DDD": 12.3}, 2: {"2": 222, "DDD": "321"}, 3: {"DDD": nil}}, []interface{}{1, 2, 3}, false},
+		{map[int]map[string]interface{}{1: {"1": 111, "DDD": 12.3}, -2: {"2": 222, "DDD": "321"}, 3: {"DDD": nil}}, []interface{}{-2, 1, 3}, false},
 		{map[string]interface{}{"A": 1, "2": 2}, []interface{}{"2", "A"}, false},
-		{map[float64]TestStructD{1: {11}, 2: {22}}, []interface{}{float64(1), float64(2)}, false},
+		{map[float64]float64{0.1: -0.1, -1.2: 1.2}, []interface{}{-1.2, 0.1}, false},
+		{map[float64]TestStructD{-1: {11}, 2: {22}}, []interface{}{float64(-1), float64(2)}, false},
 		{map[interface{}]interface{}{1: 1, 2.2: 2.22, "A": "A"}, []interface{}{1, 2.2, "A"}, false},
 
 		// struct