diff --git a/gui/gui.go b/gui/gui.go
index 01757c7..a7c0113 100644
--- a/gui/gui.go
+++ b/gui/gui.go
@@ -239,6 +239,8 @@ func (g *Gui) parseValue(node *tview.TreeNode) interface{} {
 	case Boolean:
 		b, _ := strconv.ParseBool(v)
 		return b
+	case Null:
+		return nil
 	}
 
 	return v
diff --git a/gui/tree.go b/gui/tree.go
index bd3f2e6..259f95c 100644
--- a/gui/tree.go
+++ b/gui/tree.go
@@ -95,9 +95,14 @@ func (t *Tree) AddNode(node interface{}) []*tview.TreeNode {
 		case reflect.Bool:
 			valueType = Boolean
 		default:
-			valueType = String
+			if node == nil {
+				valueType = Null
+			} else {
+				valueType = String
+			}
 		}
 
+		log.Printf("value_type:%v", valueType)
 		nodes = append(nodes, t.NewNodeWithLiteral(node).
 			SetReference(Reference{JSONType: Value, ValueType: valueType}))
 	}
@@ -105,6 +110,9 @@ func (t *Tree) AddNode(node interface{}) []*tview.TreeNode {
 }
 
 func (t *Tree) NewNodeWithLiteral(i interface{}) *tview.TreeNode {
+	if i == nil {
+		return tview.NewTreeNode("null")
+	}
 	return tview.NewTreeNode(fmt.Sprintf("%v", i))
 }
 
diff --git a/gui/type.go b/gui/type.go
index 387049c..3e02de7 100644
--- a/gui/type.go
+++ b/gui/type.go
@@ -28,6 +28,7 @@ const (
 	String
 	Float
 	Boolean
+	Null
 )
 
 var valueTypeMap = map[ValueType]string{
@@ -35,6 +36,7 @@ var valueTypeMap = map[ValueType]string{
 	String:  "string",
 	Float:   "float",
 	Boolean: "boolean",
+	Null:    "null",
 }
 
 func (v ValueType) String() string {