diff --git a/model/labels/labels.go b/model/labels/labels.go
index 6de001c3ce..8fc401564b 100644
--- a/model/labels/labels.go
+++ b/model/labels/labels.go
@@ -547,8 +547,8 @@ func (b *Builder) Get(n string) string {
 // Range calls f on each label in the Builder.
 func (b *Builder) Range(f func(l Label)) {
 	// Stack-based arrays to avoid heap allocation in most cases.
-	var addStack [1024]Label
-	var delStack [1024]string
+	var addStack [128]Label
+	var delStack [128]string
 	// Take a copy of add and del, so they are unaffected by calls to Set() or Del().
 	origAdd, origDel := append(addStack[:0], b.add...), append(delStack[:0], b.del...)
 	b.base.Range(func(l Label) {
diff --git a/model/labels/labels_string.go b/model/labels/labels_string.go
index 98db29d254..560b643db3 100644
--- a/model/labels/labels_string.go
+++ b/model/labels/labels_string.go
@@ -601,8 +601,8 @@ func (b *Builder) Get(n string) string {
 // Range calls f on each label in the Builder.
 func (b *Builder) Range(f func(l Label)) {
 	// Stack-based arrays to avoid heap allocation in most cases.
-	var addStack [1024]Label
-	var delStack [1024]string
+	var addStack [128]Label
+	var delStack [128]string
 	// Take a copy of add and del, so they are unaffected by calls to Set() or Del().
 	origAdd, origDel := append(addStack[:0], b.add...), append(delStack[:0], b.del...)
 	b.base.Range(func(l Label) {