diff --git a/core/mapping/unmarshaler.go b/core/mapping/unmarshaler.go
index fb4838c22..8d7d133b5 100644
--- a/core/mapping/unmarshaler.go
+++ b/core/mapping/unmarshaler.go
@@ -622,13 +622,19 @@ func (u *Unmarshaler) processFieldNotFromString(fieldType reflect.Type, value re
 
 		return u.fillSliceFromString(fieldType, value, mapValue, fullName)
 	case valueKind == reflect.String && derefedFieldType == durationType:
-		v, ok := mapValue.(string)
-		if !ok {
-			return fmt.Errorf("unexpected type %T, expected a string value for field %s", mapValue, fullName)
+		v, err := convertToString(mapValue, fullName)
+		if err != nil {
+			return err
 		}
+
 		return fillDurationValue(fieldType, value, v)
 	case valueKind == reflect.String && typeKind == reflect.Struct && u.implementsUnmarshaler(fieldType):
-		return u.fillUnmarshalerStruct(fieldType, value, mapValue.(string))
+		v, err := convertToString(mapValue, fullName)
+		if err != nil {
+			return err
+		}
+
+		return u.fillUnmarshalerStruct(fieldType, value, v)
 	default:
 		return u.processFieldPrimitive(fieldType, value, mapValue, opts, fullName)
 	}
diff --git a/core/mapping/unmarshaler_test.go b/core/mapping/unmarshaler_test.go
index ac9efd8ba..d9534962b 100644
--- a/core/mapping/unmarshaler_test.go
+++ b/core/mapping/unmarshaler_test.go
@@ -13,7 +13,6 @@ import (
 
 	"github.com/google/uuid"
 	"github.com/stretchr/testify/assert"
-
 	"github.com/zeromicro/go-zero/core/jsonx"
 	"github.com/zeromicro/go-zero/core/stringx"
 )
@@ -215,7 +214,7 @@ func TestUnmarshalDurationUnexpectedError(t *testing.T) {
 	var in inner
 	err = UnmarshalKey(m, &in)
 	assert.Error(t, err)
-	assert.Contains(t, err.Error(), "unexpected type")
+	assert.Contains(t, err.Error(), "expect string")
 }
 
 func TestUnmarshalDurationDefault(t *testing.T) {
@@ -6010,6 +6009,16 @@ func TestUnmarshal_Unmarshaler(t *testing.T) {
 		}, &v))
 		assert.Nil(t, v.Foo)
 	})
+
+	t.Run("json.Number", func(t *testing.T) {
+		v := struct {
+			Foo *mockUnmarshaler `json:"name"`
+		}{}
+		m := map[string]any{
+			"name": json.Number("123"),
+		}
+		assert.Error(t, UnmarshalJsonMap(m, &v))
+	})
 }
 
 func TestParseJsonStringValue(t *testing.T) {
diff --git a/core/mapping/utils.go b/core/mapping/utils.go
index 4995c3634..b59fde7f1 100644
--- a/core/mapping/utils.go
+++ b/core/mapping/utils.go
@@ -92,6 +92,15 @@ func ValidatePtr(v reflect.Value) error {
 	return nil
 }
 
+func convertToString(val any, fullName string) (string, error) {
+	v, ok := val.(string)
+	if !ok {
+		return "", fmt.Errorf("expect string for field %s, but got type %T", fullName, val)
+	}
+
+	return v, nil
+}
+
 func convertTypeFromString(kind reflect.Kind, str string) (any, error) {
 	switch kind {
 	case reflect.Bool: