diff --git a/tsdb/index/index_test.go b/tsdb/index/index_test.go
index ff22fb1c0..e6b2e890c 100644
--- a/tsdb/index/index_test.go
+++ b/tsdb/index/index_test.go
@@ -68,14 +68,14 @@ func (m mockIndex) AddSeries(ref storage.SeriesRef, l labels.Labels, chunks ...c
 	if _, ok := m.series[ref]; ok {
 		return errors.Errorf("series with reference %d already added", ref)
 	}
-	for _, lbl := range l {
+	l.Range(func(lbl labels.Label) {
 		m.symbols[lbl.Name] = struct{}{}
 		m.symbols[lbl.Value] = struct{}{}
 		if _, ok := m.postings[lbl]; !ok {
 			m.postings[lbl] = []storage.SeriesRef{}
 		}
 		m.postings[lbl] = append(m.postings[lbl], ref)
-	}
+	})
 	m.postings[allPostingsKey] = append(m.postings[allPostingsKey], ref)
 
 	s := series{l: l}
@@ -129,7 +129,7 @@ func (m mockIndex) Series(ref storage.SeriesRef, builder *labels.ScratchBuilder,
 	if !ok {
 		return errors.New("not found")
 	}
-	*lset = append((*lset)[:0], s.l...)
+	lset.CopyFrom(s.l)
 	*chks = append((*chks)[:0], s.chunks...)
 
 	return nil
@@ -322,7 +322,7 @@ func TestPostingsMany(t *testing.T) {
 		var metas []chunks.Meta
 		for it.Next() {
 			require.NoError(t, ir.Series(it.At(), &builder, &lbls, &metas))
-			got = append(got, lbls.Get("i"))
+			got = append(got, lbls.Copy().Get("i"))
 		}
 		require.NoError(t, it.Err())
 		exp := []string{}
@@ -346,10 +346,10 @@ func TestPersistence_index_e2e(t *testing.T) {
 
 	symbols := map[string]struct{}{}
 	for _, lset := range lbls {
-		for _, l := range lset {
+		lset.Range(func(l labels.Label) {
 			symbols[l.Name] = struct{}{}
 			symbols[l.Value] = struct{}{}
-		}
+		})
 	}
 
 	var input indexWriterSeriesSlice
@@ -397,14 +397,14 @@ func TestPersistence_index_e2e(t *testing.T) {
 		require.NoError(t, err)
 		require.NoError(t, mi.AddSeries(storage.SeriesRef(i), s.labels, s.chunks...))
 
-		for _, l := range s.labels {
+		s.labels.Range(func(l labels.Label) {
 			valset, ok := values[l.Name]
 			if !ok {
 				valset = map[string]struct{}{}
 				values[l.Name] = valset
 			}
 			valset[l.Value] = struct{}{}
-		}
+		})
 		postings.Add(storage.SeriesRef(i), s.labels)
 	}