diff --git a/expr/functions/transformNull/function.go b/expr/functions/transformNull/function.go
index 566aa433e..678151d98 100644
--- a/expr/functions/transformNull/function.go
+++ b/expr/functions/transformNull/function.go
@@ -10,6 +10,7 @@ import (
 
 	"github.com/go-graphite/carbonapi/expr/helper"
 	"github.com/go-graphite/carbonapi/expr/interfaces"
+	"github.com/go-graphite/carbonapi/expr/tags"
 	"github.com/go-graphite/carbonapi/expr/types"
 	"github.com/go-graphite/carbonapi/pkg/parser"
 )
@@ -88,7 +89,8 @@ func (f *transformNull) Do(ctx context.Context, e parser.Expr, from, until int64
 			name = "transformNull(" + a.Name + ")"
 		}
 
-		r := a.CopyName(name)
+		r := a.CopyLink()
+		r.Name = name
 		r.Values = make([]float64, len(a.Values))
 		r.Tags["transformNull"] = defvStr
 
@@ -109,15 +111,18 @@ func (f *transformNull) Do(ctx context.Context, e parser.Expr, from, until int64
 	if len(arg) == 0 && defaultOnAbsent {
 		values := []float64{defv, defv}
 		step := until - from
+		name := e.ToString()
+		tags := tags.ExtractTags(types.ExtractName(name))
+		tags["transformNull"] = defvStr
 		results = append(results, &types.MetricData{
 			FetchResponse: pbv3.FetchResponse{
-				Name:      e.ToString(),
+				Name:      name,
 				StartTime: from,
 				StopTime:  from + step*int64(len(values)),
 				StepTime:  step,
 				Values:    values,
 			},
-			Tags: map[string]string{"name": e.ToString()},
+			Tags: tags,
 		})
 	}
 	return results, nil
diff --git a/expr/functions/transformNull/function_test.go b/expr/functions/transformNull/function_test.go
index 59a92fbe5..d548b5a7f 100644
--- a/expr/functions/transformNull/function_test.go
+++ b/expr/functions/transformNull/function_test.go
@@ -32,7 +32,7 @@ func TestTransformNull(t *testing.T) {
 				{"metric1", 0, 1}: {types.MakeMetricData("metric1", []float64{1, math.NaN(), math.NaN(), 3, 4, 12}, 1, now)},
 			},
 			[]*types.MetricData{types.MakeMetricData("transformNull(metric1)",
-				[]float64{1, 0, 0, 3, 4, 12}, 1, now).SetTag("transformNull", "0").SetNameTag("transformNull(metric1)")},
+				[]float64{1, 0, 0, 3, 4, 12}, 1, now).SetTag("transformNull", "0").SetNameTag("metric1")},
 		},
 		{
 			`transformNull(metric1, default=5)`,
@@ -40,7 +40,7 @@ func TestTransformNull(t *testing.T) {
 				{"metric1", 0, 1}: {types.MakeMetricData("metric1", []float64{1, math.NaN(), math.NaN(), 3, 4, 12}, 1, now)},
 			},
 			[]*types.MetricData{types.MakeMetricData("transformNull(metric1,5)",
-				[]float64{1, 5, 5, 3, 4, 12}, 1, now).SetTag("transformNull", "5").SetNameTag("transformNull(metric1,5)")},
+				[]float64{1, 5, 5, 3, 4, 12}, 1, now).SetTag("transformNull", "5").SetNameTag("metric1")},
 		},
 		{
 			`transformNull(metric1, default=5, referenceSeries=metric2.*)`,
@@ -51,13 +51,22 @@ func TestTransformNull(t *testing.T) {
 					types.MakeMetricData("metric2.bar", []float64{1, math.NaN(), math.NaN(), 3, 4, 12}, 1, now)},
 			},
 			[]*types.MetricData{types.MakeMetricData("transformNull(metric1,5)",
-				[]float64{1, 5, math.NaN(), 5, 4, 12}, 1, now).SetTag("transformNull", "5").SetNameTag("transformNull(metric1,5)")},
+				[]float64{1, 5, math.NaN(), 5, 4, 12}, 1, now).SetTag("transformNull", "5").SetNameTag("metric1")},
 		},
 		{
 			`transformNull(metric1, default=5, defaultOnAbsent=True)`,
 			map[parser.MetricRequest][]*types.MetricData{},
 			[]*types.MetricData{types.MakeMetricData("transformNull(metric1, default=5, defaultOnAbsent=True)",
-				[]float64{5, 5}, 1, 0).SetNameTag(`transformNull(metric1, default=5, defaultOnAbsent=True)`)},
+				[]float64{5, 5}, 1, 0).SetTag("transformNull", "5").SetNameTag(`metric1`)},
+		},
+		// tagged metric
+		{
+			`transformNull(seriesByTag('name=metric1'), 0)`,
+			map[parser.MetricRequest][]*types.MetricData{
+				{"seriesByTag('name=metric1')", 0, 1}: {types.MakeMetricData("metric1;env=prod", []float64{1, math.NaN(), math.NaN(), 3, 4, 12}, 1, now)},
+			},
+			[]*types.MetricData{types.MakeMetricData("transformNull(metric1;env=prod,0)",
+				[]float64{1, 0, 0, 3, 4, 12}, 1, now).SetTag("transformNull", "0").SetNameTag("metric1").SetTag("env", "prod")},
 		},
 	}
 
diff --git a/expr/types/types.go b/expr/types/types.go
index 9df402930..3f5fb764c 100644
--- a/expr/types/types.go
+++ b/expr/types/types.go
@@ -427,12 +427,17 @@ func (r *MetricData) Copy(includeValues bool) *MetricData {
 	}
 }
 
+func CopyLink(tags map[string]string) map[string]string {
+	newTags := make(map[string]string)
+	for k, v := range tags {
+		newTags[k] = v
+	}
+	return newTags
+}
+
 // CopyLink returns the copy of MetricData, Values not copied and link from parent. Tags map are copied
 func (r *MetricData) CopyLink() *MetricData {
-	tags := make(map[string]string)
-	for k, v := range r.Tags {
-		tags[k] = v
-	}
+	tags := CopyLink(r.Tags)
 
 	return &MetricData{
 		FetchResponse: pb.FetchResponse{