diff --git a/src/go/ast/commentmap.go b/src/go/ast/commentmap.go
index 9f81493f64..4196e475d9 100644
--- a/src/go/ast/commentmap.go
+++ b/src/go/ast/commentmap.go
@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"go/token"
 	"sort"
+	"strings"
 )
 
 type byPos []*CommentGroup
@@ -311,7 +312,7 @@ func (cmap CommentMap) String() string {
 	}
 	sort.Sort(byInterval(nodes))
 
-	var buf bytes.Buffer
+	var buf strings.Builder
 	fmt.Fprintln(&buf, "CommentMap {")
 	for _, node := range nodes {
 		comment := cmap[node]
diff --git a/src/go/ast/scope.go b/src/go/ast/scope.go
index 02691f8e54..8882212007 100644
--- a/src/go/ast/scope.go
+++ b/src/go/ast/scope.go
@@ -7,9 +7,9 @@
 package ast
 
 import (
-	"bytes"
 	"fmt"
 	"go/token"
+	"strings"
 )
 
 // A Scope maintains the set of named language entities declared
@@ -46,7 +46,7 @@ func (s *Scope) Insert(obj *Object) (alt *Object) {
 
 // Debugging support
 func (s *Scope) String() string {
-	var buf bytes.Buffer
+	var buf strings.Builder
 	fmt.Fprintf(&buf, "scope %p {", s)
 	if s != nil && len(s.Objects) > 0 {
 		fmt.Fprintln(&buf)