diff --git a/component/outbound/filter.go b/component/outbound/filter.go
index 94265d7..be83788 100644
--- a/component/outbound/filter.go
+++ b/component/outbound/filter.go
@@ -51,6 +51,11 @@ func NewDialerSetFromLinks(option *dialer.GlobalOption, tagToNodeList map[string
 }
 
 func (s *DialerSet) filterHit(dialer *dialer.Dialer, filters []*config_parser.Function) (hit bool, err error) {
+	if len(filters) == 0 {
+		// No filter.
+		return true, nil
+	}
+
 	// Example
 	// filter: name(regex:'^.*hk.*$', keyword:'sg') && name(keyword:'disney')
 	// filter: !name(regex: 'HK|TW|SG') && name(keyword: disney)
diff --git a/config/config.go b/config/config.go
index b6ca01c..a2b0fdd 100644
--- a/config/config.go
+++ b/config/config.go
@@ -32,7 +32,7 @@ type Group struct {
 }
 
 type GroupParam struct {
-	Filter []*config_parser.Function `mapstructure:"filter" required:""`
+	Filter []*config_parser.Function `mapstructure:"filter"`
 	Policy interface{}               `mapstructure:"policy" required:""`
 }