diff --git a/gen/parse_test.go b/gen/parse_test.go
index b3532ef..dd1def6 100644
--- a/gen/parse_test.go
+++ b/gen/parse_test.go
@@ -132,8 +132,7 @@ func BenchmarkParseTreeInfo(b *testing.B) {
 	require.NoError(b, err)
 	tree := x.Learner.GradientBooster.Model.Trees[0]
 
-	b.ResetTimer()
-	for range b.N {
+	for b.Loop() {
 		_, err := parseTreeInfo(tree)
 		require.NoError(b, err)
 	}
diff --git a/gen/templates.go b/gen/templates.go
index b11c00e..af44e05 100644
--- a/gen/templates.go
+++ b/gen/templates.go
@@ -4,6 +4,7 @@ import (
 	"bytes"
 	_ "embed"
 	"fmt"
+	"strings"
 	"text/template"
 )
 
@@ -54,11 +55,11 @@ func newRenderer() (*renderer, error) {
 }
 
 func indent(level int) string {
-	var s string
+	var sb strings.Builder
 	for range level + 1 {
-		s += "\t"
+		sb.WriteString("\t")
 	}
-	return s
+	return sb.String()
 }
 
 type decisionNodeParams struct {