diff --git a/cmd/promtool/rules_test.go b/cmd/promtool/rules_test.go
index caa930616..fb582ed0d 100644
--- a/cmd/promtool/rules_test.go
+++ b/cmd/promtool/rules_test.go
@@ -100,7 +100,7 @@ func TestBackfillRuleIntegration(t *testing.T) {
 				require.Equal(t, 1, len(gRules))
 				require.Equal(t, "rule1", gRules[0].Name())
 				require.Equal(t, "ruleExpr", gRules[0].Query().String())
-				require.Equal(t, 1, len(gRules[0].Labels()))
+				require.Equal(t, 1, gRules[0].Labels().Len())
 
 				group2 := ruleImporter.groups[path2+";group2"]
 				require.NotNil(t, group2)
@@ -109,7 +109,7 @@ func TestBackfillRuleIntegration(t *testing.T) {
 				require.Equal(t, 2, len(g2Rules))
 				require.Equal(t, "grp2_rule1", g2Rules[0].Name())
 				require.Equal(t, "grp2_rule1_expr", g2Rules[0].Query().String())
-				require.Equal(t, 0, len(g2Rules[0].Labels()))
+				require.Equal(t, 0, g2Rules[0].Labels().Len())
 
 				// Backfill all recording rules then check the blocks to confirm the correct data was created.
 				errs = ruleImporter.importAll(ctx)
@@ -132,12 +132,12 @@ func TestBackfillRuleIntegration(t *testing.T) {
 				for selectedSeries.Next() {
 					seriesCount++
 					series := selectedSeries.At()
-					if len(series.Labels()) != 3 {
-						require.Equal(t, 2, len(series.Labels()))
+					if series.Labels().Len() != 3 {
+						require.Equal(t, 2, series.Labels().Len())
 						x := labels.FromStrings("__name__", "grp2_rule1", "name1", "val1")
 						require.Equal(t, x, series.Labels())
 					} else {
-						require.Equal(t, 3, len(series.Labels()))
+						require.Equal(t, 3, series.Labels().Len())
 					}
 					it := series.Iterator(nil)
 					for it.Next() == chunkenc.ValFloat {