diff --git a/test/main.go b/test/main.go
index 58b8986..28edad6 100644
--- a/test/main.go
+++ b/test/main.go
@@ -126,14 +126,15 @@ func main() {
 	//	ExampleOmit()
 	//}
 
-	fmt.Println(filter.Omit("1", User{}))
-	fmt.Println(filter.Omit("1", User{}))
-	fmt.Println(filter.Omit("1", User{}))
-	fmt.Println(filter.Omit("1", User{}))
-	fmt.Println(filter.Omit("1", User{}))
-	fmt.Println(filter.Omit("1", User{}))
-	fmt.Println(filter.Omit("1", User{}))
-	fmt.Println(filter.Omit("1", User{}))
+	//fmt.Println(filter.Omit("1", User{}))
+	//fmt.Println(filter.Omit("1", User{}))
+	//fmt.Println(filter.Omit("1", User{}))
+	//fmt.Println(filter.Omit("1", User{}))
+	//fmt.Println(filter.Omit("1", User{}))
+	//fmt.Println(filter.Omit("1", User{}))
+	//fmt.Println(filter.Omit("1", User{}))
+	//fmt.Println(filter.Omit("1", User{}))
+	TestNilValue()
 
 }
 
diff --git a/test/nil_value.go b/test/nil_value.go
new file mode 100644
index 0000000..6f62dd9
--- /dev/null
+++ b/test/nil_value.go
@@ -0,0 +1,27 @@
+package main
+
+import (
+	"fmt"
+	"github.com/liu-cn/json-filter/filter"
+)
+
+func TestNilValue() {
+	var a *T
+	var c *T
+	var el = map[string]interface{}{
+		"a": a, // a: nil ptr
+		"b": 1,
+		"c": map[string]interface{}{
+			"bb": nil,
+			"dd": c, // dd: nil ptr
+		},
+	}
+
+	fmt.Println(filter.Select("test", el))
+	//{"a":null,"b":1,"c":{"bb":null,"dd":null}}
+
+}
+
+type T struct {
+	A string `json:"a,select(test)"`
+}