diff --git a/app/vmselect/promql/exec_test.go b/app/vmselect/promql/exec_test.go
index 8432260295..6db7ec11db 100644
--- a/app/vmselect/promql/exec_test.go
+++ b/app/vmselect/promql/exec_test.go
@@ -7261,6 +7261,17 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`range_trim_outliers(time() > 1200)`, func(t *testing.T) {
+		t.Parallel()
+		q := `range_trim_outliers(0.5, time() > 1200)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{nan, nan, nan, 1600, 1800, nan},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`range_trim_spikes()`, func(t *testing.T) {
 		t.Parallel()
 		q := `range_trim_spikes(0.2, time())`
@@ -7272,6 +7283,17 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`range_trim_spikes(time() > 1200 <= 1800)`, func(t *testing.T) {
+		t.Parallel()
+		q := `range_trim_spikes(0.2, time() > 1200 <= 1800)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{nan, nan, nan, 1600, nan, nan},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`range_trim_zscore()`, func(t *testing.T) {
 		t.Parallel()
 		q := `range_trim_zscore(0.9, time())`
@@ -7283,6 +7305,17 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`range_trim_zscore(time() > 1200 <= 1800)`, func(t *testing.T) {
+		t.Parallel()
+		q := `range_trim_zscore(0.9, time() > 1200 <= 1800)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{nan, nan, nan, 1600, nan, nan},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`range_zscore()`, func(t *testing.T) {
 		t.Parallel()
 		q := `round(range_zscore(time()), 0.1)`
@@ -7294,6 +7327,17 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`range_zscore(time() > 1200 < 1800)`, func(t *testing.T) {
+		t.Parallel()
+		q := `round(range_zscore(time() > 1200 < 1800), 0.1)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{nan, nan, -1, 1, nan, nan},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`range_quantile(0.5)`, func(t *testing.T) {
 		t.Parallel()
 		q := `range_quantile(0.5, time())`
@@ -7305,6 +7349,17 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`range_quantile(0.5, time() > 1200 < 2000)`, func(t *testing.T) {
+		t.Parallel()
+		q := `range_quantile(0.5, time() > 1200 < 2000)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{1600, 1600, 1600, 1600, 1600, 1600},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`range_stddev()`, func(t *testing.T) {
 		t.Parallel()
 		q := `round(range_stddev(time()),0.01)`
@@ -7316,6 +7371,17 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`range_stddev(time() > 1200 < 1800)`, func(t *testing.T) {
+		t.Parallel()
+		q := `round(range_stddev(time() > 1200 < 1800),0.01)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{100, 100, 100, 100, 100, 100},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`range_stdvar()`, func(t *testing.T) {
 		t.Parallel()
 		q := `round(range_stdvar(time()),0.01)`
@@ -7327,6 +7393,17 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`range_stdvar(time() > 1200 < 1800)`, func(t *testing.T) {
+		t.Parallel()
+		q := `round(range_stdvar(time() > 1200 < 1800),0.01)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{10000, 10000, 10000, 10000, 10000, 10000},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`range_median()`, func(t *testing.T) {
 		t.Parallel()
 		q := `range_median(time())`
@@ -7687,6 +7764,17 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`running_min(abs(1500-time()) < 400 > 100)`, func(t *testing.T) {
+		t.Parallel()
+		q := `running_min(abs(1500-time()) < 400 > 100)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{nan, 300, 300, 300, 300, 300},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`running_max(abs(1300-time()))`, func(t *testing.T) {
 		t.Parallel()
 		q := `running_max(abs(1300-time()))`
@@ -7698,6 +7786,17 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`running_max(abs(1300-time()) > 300 < 700)`, func(t *testing.T) {
+		t.Parallel()
+		q := `running_max(abs(1300-time()) > 300 < 700)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{nan, nan, nan, nan, 500, 500},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`running_sum(1)`, func(t *testing.T) {
 		t.Parallel()
 		q := `running_sum(1)`
@@ -7720,6 +7819,17 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`running_sum(time() > 1.2 < 1.8)`, func(t *testing.T) {
+		t.Parallel()
+		q := `running_sum(time()/1e3 > 1.2 < 1.8)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{nan, nan, 1.4, 3, 3, 3},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`running_avg(time())`, func(t *testing.T) {
 		t.Parallel()
 		q := `running_avg(time())`
@@ -7731,6 +7841,17 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`running_avg(time() > 1200 < 1800)`, func(t *testing.T) {
+		t.Parallel()
+		q := `running_avg(time() > 1200 < 1800)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{nan, nan, 1400, 1500, 1500, 1500},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`smooth_exponential(time(), 1)`, func(t *testing.T) {
 		t.Parallel()
 		q := `smooth_exponential(time(), 1)`
@@ -7811,6 +7932,17 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`range_min(time() > 1200 < 1800)`, func(t *testing.T) {
+		t.Parallel()
+		q := `range_min(time() > 1200 < 1800)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{1400, 1400, 1400, 1400, 1400, 1400},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`range_normalize(time(),alias(-time(),"negative"))`, func(t *testing.T) {
 		t.Parallel()
 		q := `range_normalize(time(),alias(-time(), "negative"))`
@@ -7828,6 +7960,23 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r1, r2}
 		f(q, resultExpected)
 	})
+	t.Run(`range_normalize(time() > 1200 < 1800,alias(-(time() > 1400 < 2000),"negative"))`, func(t *testing.T) {
+		t.Parallel()
+		q := `range_normalize(time() > 1200 < 1800,alias(-(time() > 1200 < 2000), "negative"))`
+		r1 := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{nan, nan, 0, 1, nan, nan},
+			Timestamps: timestampsExpected,
+		}
+		r2 := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{nan, nan, 1, 0.5, 0, nan},
+			Timestamps: timestampsExpected,
+		}
+		r2.MetricName.MetricGroup = []byte("negative")
+		resultExpected := []netstorage.Result{r1, r2}
+		f(q, resultExpected)
+	})
 	t.Run(`range_first(time())`, func(t *testing.T) {
 		t.Parallel()
 		q := `range_first(time())`
@@ -7839,6 +7988,17 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`range_first(time() > 1200 < 1800)`, func(t *testing.T) {
+		t.Parallel()
+		q := `range_first(time() > 1200 < 1800)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{1400, 1400, 1400, 1400, 1400, 1400},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`range_mad(time())`, func(t *testing.T) {
 		t.Parallel()
 		q := `range_mad(time())`
@@ -7850,6 +8010,17 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`range_mad(time() > 1200 < 1800)`, func(t *testing.T) {
+		t.Parallel()
+		q := `range_mad(time() > 1200 < 1800)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{100, 100, 100, 100, 100, 100},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`range_max(time())`, func(t *testing.T) {
 		t.Parallel()
 		q := `range_max(time())`
@@ -7861,6 +8032,39 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`range_max(time() > 1200 < 1800)`, func(t *testing.T) {
+		t.Parallel()
+		q := `range_max(time() > 1200 < 1800)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{1600, 1600, 1600, 1600, 1600, 1600},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
+	t.Run(`range_sum(time())`, func(t *testing.T) {
+		t.Parallel()
+		q := `range_sum(time())`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{9000, 9000, 9000, 9000, 9000, 9000},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
+	t.Run(`range_sum(time() > 1200 < 1800)`, func(t *testing.T) {
+		t.Parallel()
+		q := `range_sum(time() > 1200 < 1800)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{3000, 3000, 3000, 3000, 3000, 3000},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`range_last(time())`, func(t *testing.T) {
 		t.Parallel()
 		q := `range_last(time())`
@@ -7872,6 +8076,17 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`range_last(time() > 1200 < 1800)`, func(t *testing.T) {
+		t.Parallel()
+		q := `range_last(time() > 1200 < 1800)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{1600, 1600, 1600, 1600, 1600, 1600},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`range_linear_regression(time())`, func(t *testing.T) {
 		t.Parallel()
 		q := `range_linear_regression(time())`
@@ -7894,6 +8109,17 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`range_linear_regression(time() > 1200 < 1800)`, func(t *testing.T) {
+		t.Parallel()
+		q := `range_linear_regression(time() > 1200 < 1800)`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{1000, 1200, 1400, 1600, 1800, 2000},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`range_linear_regression(100/time())`, func(t *testing.T) {
 		t.Parallel()
 		q := `sort_desc(round((
diff --git a/app/vmselect/promql/transform.go b/app/vmselect/promql/transform.go
index 9cac71c790..a0754d692b 100644
--- a/app/vmselect/promql/transform.go
+++ b/app/vmselect/promql/transform.go
@@ -1544,10 +1544,8 @@ func transformRangeFirst(tfa *transformFuncArg) ([]*timeseries, error) {
 			continue
 		}
 		vFirst := values[0]
-		for i, v := range values {
-			if math.IsNaN(v) {
-				continue
-			}
+		values = ts.Values
+		for i := range values {
 			values[i] = vFirst
 		}
 	}
@@ -1571,10 +1569,8 @@ func setLastValues(tss []*timeseries) {
 			continue
 		}
 		vLast := values[len(values)-1]
-		for i, v := range values {
-			if math.IsNaN(v) {
-				continue
-			}
+		values = ts.Values
+		for i := range values {
 			values[i] = vLast
 		}
 	}
diff --git a/docs/changelog/CHANGELOG.md b/docs/changelog/CHANGELOG.md
index 99abd04619..47188d071f 100644
--- a/docs/changelog/CHANGELOG.md
+++ b/docs/changelog/CHANGELOG.md
@@ -40,6 +40,8 @@ See also [LTS releases](https://docs.victoriametrics.com/lts-releases/).
 * BUGFIX: [vmalert](https://docs.victoriametrics.com/vmalert): do not send notifications without labels to Alertmanager. Such notifications are rejected by Alertmanager anyway. Before, vmalert could send alert notifications even if no label-value pairs left after applying `alert_relabel_configs` from [notifier config](https://docs.victoriametrics.com/vmalert/#notifier-configuration-file).
 * BUGFIX: [vmalert](https://docs.victoriametrics.com/vmalert/): properly update value of variable `$activeAt` in rules annotation during replay mode. Before, `$activeAt` could have provided incorrect values during replay.
 * BUGFIX: [MetricsQL](https://docs.victoriametrics.com/metricsql/): properly handle `c1 AND c2` and `c1 OR c1` queries for constants `c1` and `c2`. Previously such queries could return unexpected results. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/6637).
+* BUGFIX: [MetricsQL](https://docs.victoriametrics.com/metricsql/): consistently return the first non-`NaN` value from [`range_first`](https://docs.victoriametrics.com/metricsql/#range_first) function across all the returned data points. Previously `NaN` data points weren't replaced with the first non-`NaN` value.
+* BUGFIX: [MetricsQL](https://docs.victoriametrics.com/metricsql/): consistently return the last non-`NaN` value from [`range_last`](https://docs.victoriametrics.com/metricsql/#range_last) function across all the returned data points. Previously `NaN` data points weren't replaced with the last non-`NaN` value.
 * BUGFIX: all VictoriaMetrics components: increase default value of `-loggerMaxArgLen` cmd-line flag from 1000 to 5000. This should improve visibility on errors produced by very long queries.
 
 ## [v1.103.0](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.103.0)