diff --git a/app/vmselect/promql/exec_test.go b/app/vmselect/promql/exec_test.go
index a31950d266..0aab3b13aa 100644
--- a/app/vmselect/promql/exec_test.go
+++ b/app/vmselect/promql/exec_test.go
@@ -2135,6 +2135,21 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`label_join dst_label is equal to src_label`, func(t *testing.T) {
+		t.Parallel()
+		q := `label_join(label_join(time(), "bar", "sep1", "a", "b"), "bar", "sep2", "a", "bar")`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{1000, 1200, 1400, 1600, 1800, 2000},
+			Timestamps: timestampsExpected,
+		}
+		r.MetricName.Tags = []storage.Tag{{
+			Key:   []byte("bar"),
+			Value: []byte("sep2sep1"),
+		}}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`label_value()`, func(t *testing.T) {
 		t.Parallel()
 		q := `with (
diff --git a/app/vmselect/promql/transform.go b/app/vmselect/promql/transform.go
index a436d52dd0..eaccde4529 100644
--- a/app/vmselect/promql/transform.go
+++ b/app/vmselect/promql/transform.go
@@ -1923,8 +1923,7 @@ func transformLabelJoin(tfa *transformFuncArg) ([]*timeseries, error) {
 	for _, ts := range rvs {
 		mn := &ts.MetricName
 		dstValue := getDstValue(mn, dstLabel)
-		b := *dstValue
-		b = b[:0]
+		var b []byte
 		for j, srcLabel := range srcLabels {
 			srcValue := mn.GetTagValue(srcLabel)
 			b = append(b, srcValue...)
diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index e07764e202..1cf6999027 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -17,6 +17,7 @@ The following `tip` changes can be tested by building VictoriaMetrics components
   or [/api/v1/query_range](https://docs.victoriametrics.com/keyconcepts/#range-query). See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5795).
 * BUGFIX: [Single-node VictoriaMetrics](https://docs.victoriametrics.com/) and `vmselect` in [VictoriaMetrics cluster](https://docs.victoriametrics.com/cluster-victoriametrics/): fixed floating-point error when parsing time in RFC3339 format. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5801) for details.
 * BUGFIX: [vmalert](https://docs.victoriametrics.com/#vmalert): consistently sort groups by name and filename on `/groups` page in UI. This should prevent non-deterministic sorting for groups with identical names.
+* BUGFIX: [MetricsQL](https://docs.victoriametrics.com/MetricsQL.html): properly construct the destination label in [label_join](https://docs.victoriametrics.com/metricsql/#label_join) if it is used as source label. See this [issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5881) for details.
 
 ## [v1.93.12](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.93.12)