diff --git a/app/vmselect/promql/exec_test.go b/app/vmselect/promql/exec_test.go
index 6dfeed585..48a5b9fe8 100644
--- a/app/vmselect/promql/exec_test.go
+++ b/app/vmselect/promql/exec_test.go
@@ -369,6 +369,17 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run("timestamp(time()>=1600)", func(t *testing.T) {
+		t.Parallel()
+		q := `timestamp(time()>=1600)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{nan, nan, nan, 1600, 1800, 2000},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run("time()/100", func(t *testing.T) {
 		t.Parallel()
 		q := `time()/100`
diff --git a/app/vmselect/promql/transform.go b/app/vmselect/promql/transform.go
index 70e29201b..388b91276 100644
--- a/app/vmselect/promql/transform.go
+++ b/app/vmselect/promql/transform.go
@@ -1121,7 +1121,10 @@ func transformTimestamp(tfa *transformFuncArg) ([]*timeseries, error) {
 		ts.MetricName.ResetMetricGroup()
 		values := ts.Values
 		for i, t := range ts.Timestamps {
-			values[i] = float64(t) / 1e3
+			v := values[i]
+			if !math.IsNaN(v) {
+				values[i] = float64(t) / 1e3
+			}
 		}
 	}
 	return rvs, nil