diff --git a/model/insight/metric_data.go b/model/insight/metric_data.go
index fcc6e37b..bad438b5 100644
--- a/model/insight/metric_data.go
+++ b/model/insight/metric_data.go
@@ -85,7 +85,7 @@ func (m *Metric) ValidateSortKey() error {
 		if v, ok := mm[sortItem.Key]; !ok && !util.StringInArray([]string{"_key", "_count"}, sortItem.Key){
 			return fmt.Errorf("unknown sort key [%s]", sortItem.Key)
 		}else{
-			if v.Statistic == "derivative" {
+			if v != nil && v.Statistic == "derivative" {
 				return fmt.Errorf("can not sort by pipeline agg [%s]", v.Statistic)
 			}
 		}