diff --git a/src/io/example_test.go b/src/io/example_test.go
index 419e449982..818020e9de 100644
--- a/src/io/example_test.go
+++ b/src/io/example_test.go
@@ -5,7 +5,6 @@
 package io_test
 
 import (
-	"bytes"
 	"fmt"
 	"io"
 	"log"
@@ -239,7 +238,7 @@ func ExampleSeeker_Seek() {
 func ExampleMultiWriter() {
 	r := strings.NewReader("some io.Reader stream to be read\n")
 
-	var buf1, buf2 bytes.Buffer
+	var buf1, buf2 strings.Builder
 	w := io.MultiWriter(&buf1, &buf2)
 
 	if _, err := io.Copy(w, r); err != nil {
diff --git a/src/io/multi_test.go b/src/io/multi_test.go
index 679312c23b..7a24a8afc5 100644
--- a/src/io/multi_test.go
+++ b/src/io/multi_test.go
@@ -228,7 +228,7 @@ func TestMultiReaderCopy(t *testing.T) {
 
 // Test that MultiWriter copies the input slice and is insulated from future modification.
 func TestMultiWriterCopy(t *testing.T) {
-	var buf bytes.Buffer
+	var buf strings.Builder
 	slice := []Writer{&buf}
 	w := MultiWriter(slice...)
 	slice[0] = nil