diff --git a/proxy/router/numkey.go b/proxy/router/numkey.go
index 4c9e21b9..b990dcbe 100644
--- a/proxy/router/numkey.go
+++ b/proxy/router/numkey.go
@@ -36,7 +36,7 @@ type NumKeyRange struct {
 }
 
 func (kr NumKeyRange) MapKey() string {
-	return fmt.Sprintf("%d-%d", kr.String(), kr.End)
+	return fmt.Sprintf("%d-%d", kr.Start, kr.End)
 }
 
 func (kr NumKeyRange) Contains(i int64) bool {