diff --git a/prometheus/histogram.go b/prometheus/histogram.go
index f88da707b..45f35177e 100644
--- a/prometheus/histogram.go
+++ b/prometheus/histogram.go
@@ -360,7 +360,7 @@ func (h *histogram) Write(out *dto.Metric) error {
 
 	his.Bucket = buckets
 	out.Histogram = his
-	out.Label = h.labelPairs
+	out.Label = copyLabelPairs(h.labelPairs)
 
 	// Finally add all the cold counts to the new hot counts and reset the cold counts.
 	atomic.AddUint64(&hotCounts.count, count)
diff --git a/prometheus/registry.go b/prometheus/registry.go
index f98c81a86..540759b01 100644
--- a/prometheus/registry.go
+++ b/prometheus/registry.go
@@ -872,7 +872,7 @@ func checkMetricConsistency(
 	h = hashAddByte(h, separatorByte)
 	// Make sure label pairs are sorted. We depend on it for the consistency
 	// check.
-	sort.Sort(labelPairSorter(dtoMetric.Label))
+	sort.Stable(labelPairSorter(dtoMetric.Label))
 	for _, lp := range dtoMetric.Label {
 		h = hashAdd(h, lp.GetName())
 		h = hashAddByte(h, separatorByte)
diff --git a/prometheus/registry_test.go b/prometheus/registry_test.go
index a96cb10a6..5f0748242 100644
--- a/prometheus/registry_test.go
+++ b/prometheus/registry_test.go
@@ -791,7 +791,7 @@ func TestHistogramVecRegisterGatherConcurrency(t *testing.T) {
 				Help:        "This helps testing.",
 				ConstLabels: prometheus.Labels{"foo": "bar"},
 			},
-			[]string{"one", "two", "three"},
+			[]string{"one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen"},
 		)
 		labelValues = []string{"a", "b", "c", "alpha", "beta", "gamma", "aleph", "beth", "gimel"}
 		quit        = make(chan struct{})
@@ -810,6 +810,19 @@ func TestHistogramVecRegisterGatherConcurrency(t *testing.T) {
 					labelValues[rand.Intn(len(labelValues))],
 					labelValues[rand.Intn(len(labelValues))],
 					labelValues[rand.Intn(len(labelValues))],
+					labelValues[rand.Intn(len(labelValues))],
+					labelValues[rand.Intn(len(labelValues))],
+					labelValues[rand.Intn(len(labelValues))],
+					labelValues[rand.Intn(len(labelValues))],
+					labelValues[rand.Intn(len(labelValues))],
+					labelValues[rand.Intn(len(labelValues))],
+					labelValues[rand.Intn(len(labelValues))],
+					labelValues[rand.Intn(len(labelValues))],
+					labelValues[rand.Intn(len(labelValues))],
+					labelValues[rand.Intn(len(labelValues))],
+					labelValues[rand.Intn(len(labelValues))],
+					labelValues[rand.Intn(len(labelValues))],
+					labelValues[rand.Intn(len(labelValues))],
 				).Observe(obs)
 			}
 		}
@@ -848,7 +861,7 @@ func TestHistogramVecRegisterGatherConcurrency(t *testing.T) {
 					if len(g) != 1 {
 						t.Error("Gathered unexpected number of metric families:", len(g))
 					}
-					if len(g[0].Metric[0].Label) != 4 {
+					if len(g[0].Metric[0].Label) != 17 {
 						t.Error("Gathered unexpected number of label pairs:", len(g[0].Metric[0].Label))
 					}
 				}
@@ -869,7 +882,7 @@ func TestHistogramVecRegisterGatherConcurrency(t *testing.T) {
 	go gather()
 	go observe()
 
-	time.Sleep(time.Second)
+	time.Sleep(2 * time.Second)
 	close(quit)
 	wg.Wait()
 }
diff --git a/prometheus/value.go b/prometheus/value.go
index eb248f108..35d0ba790 100644
--- a/prometheus/value.go
+++ b/prometheus/value.go
@@ -125,7 +125,7 @@ func populateMetric(
 	labelPairs []*dto.LabelPair,
 	m *dto.Metric,
 ) error {
-	m.Label = labelPairs
+	m.Label = copyLabelPairs(labelPairs)
 	switch t {
 	case CounterValue:
 		m.Counter = &dto.Counter{Value: proto.Float64(v)}
@@ -160,3 +160,15 @@ func makeLabelPairs(desc *Desc, labelValues []string) []*dto.LabelPair {
 	sort.Sort(labelPairSorter(labelPairs))
 	return labelPairs
 }
+
+func copyLabelPairs(source []*dto.LabelPair) []*dto.LabelPair {
+	labelPairs := make([]*dto.LabelPair, 0, len(source))
+	for _, pair := range source {
+		labelPairs = append(labelPairs, &dto.LabelPair{
+			Name:  pair.Name,
+			Value: pair.Value,
+		})
+	}
+	// shouldn't need sorting, as it should already be sorted
+	return labelPairs
+}