diff --git a/model/labels/labels_common.go b/model/labels/labels_common.go
index a6945a0cae..4d5cee7ed1 100644
--- a/model/labels/labels_common.go
+++ b/model/labels/labels_common.go
@@ -224,6 +224,7 @@ func (b *Builder) Range(f func(l Label)) {
 	}
 }
 
+// Contains returns true if the label name n is present in s, otherwise false.
 func Contains(s []Label, n string) bool {
 	for _, a := range s {
 		if a.Name == n {