diff --git a/metric/metric.go b/metric/metric.go
index be8c2bb..4c69c54 100644
--- a/metric/metric.go
+++ b/metric/metric.go
@@ -144,6 +144,10 @@ func init() {
 func newMetricImpl(mt MetricType, name string, help string, constLabels map[string]string) (writer MetricWriter) {
 	hash := md5.New()
 	hash.Write([]byte(name))
+	for k, v := range constLabels {
+		hash.Write([]byte(k))
+		hash.Write([]byte(v))
+	}
 
 	key := hex.EncodeToString(hash.Sum(nil))[:metric_key_size]
 	temp, _ := json.Marshal(MetricDescription{