diff --git a/app/vmselect/promql/exec_test.go b/app/vmselect/promql/exec_test.go
index d98901bc9..6364a5183 100644
--- a/app/vmselect/promql/exec_test.go
+++ b/app/vmselect/promql/exec_test.go
@@ -574,6 +574,30 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`clamp_max(alias(time(),"foobar"), 1400)`, func(t *testing.T) {
+		t.Parallel()
+		q := `clamp_max(alias(time(), "foobar"), 1400)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{1000, 1200, 1400, 1400, 1400, 1400},
+			Timestamps: timestampsExpected,
+		}
+		r.MetricName.MetricGroup = []byte("foobar")
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
+	t.Run(`CLAmp_MAx(alias(time(),"foobar"), 1400)`, func(t *testing.T) {
+		t.Parallel()
+		q := `CLAmp_MAx(alias(time(), "foobar"), 1400)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{1000, 1200, 1400, 1400, 1400, 1400},
+			Timestamps: timestampsExpected,
+		}
+		r.MetricName.MetricGroup = []byte("foobar")
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run("clamp_min(time(), -time()+3000)", func(t *testing.T) {
 		t.Parallel()
 		q := `clamp_min(time(), -time()+2500)`
diff --git a/app/vmselect/promql/transform.go b/app/vmselect/promql/transform.go
index c09b2e082..bc04a9f89 100644
--- a/app/vmselect/promql/transform.go
+++ b/app/vmselect/promql/transform.go
@@ -125,7 +125,8 @@ func newTransformFuncOneArg(tf func(v float64) float64) transformFunc {
 }
 
 func doTransformValues(arg []*timeseries, tf func(values []float64), fe *funcExpr) ([]*timeseries, error) {
-	keepMetricGroup := transformFuncsKeepMetricGroup[fe.Name]
+	name := strings.ToLower(fe.Name)
+	keepMetricGroup := transformFuncsKeepMetricGroup[name]
 	for _, ts := range arg {
 		if !keepMetricGroup {
 			ts.MetricName.ResetMetricGroup()