diff --git a/app/vmalert/rule/group_timing_test.go b/app/vmalert/rule/group_timing_test.go
index c233ed34d..94399c490 100644
--- a/app/vmalert/rule/group_timing_test.go
+++ b/app/vmalert/rule/group_timing_test.go
@@ -11,7 +11,7 @@ import (
 func BenchmarkGetStaleSeries(b *testing.B) {
 	ts := time.Now()
 	n := 100
-	payload := make([]prompbmarshal.TimeSeries, n)
+	payload := make([]prompbmarshal.TimeSeries, 0, n)
 	for i := 0; i < n; i++ {
 		s := fmt.Sprintf("%d", i)
 		labels := toPromLabels(b,
diff --git a/lib/streamaggr/streamaggr_timing_test.go b/lib/streamaggr/streamaggr_timing_test.go
index 5901e56ad..de7c49c1b 100644
--- a/lib/streamaggr/streamaggr_timing_test.go
+++ b/lib/streamaggr/streamaggr_timing_test.go
@@ -79,7 +79,7 @@ func newBenchAggregators(outputs []string, pushFunc PushFunc) *Aggregators {
 }
 
 func newBenchSeries(seriesCount int) []prompbmarshal.TimeSeries {
-	a := make([]string, seriesCount)
+	a := make([]string, 0, seriesCount)
 	for j := 0; j < seriesCount; j++ {
 		s := fmt.Sprintf(`http_requests_total{path="/foo/%d",job="foo_%d",instance="bar",pod="pod-123232312",namespace="kube-foo-bar",node="node-123-3434-443",`+
 			`some_other_label="foo-bar-baz",environment="prod",label1="value1",label2="value2",label3="value3"} %d`, j, j%100, j*1000)