diff --git a/src/unicode/utf8/example_test.go b/src/unicode/utf8/example_test.go
index 5cd931d242..fe434c9476 100644
--- a/src/unicode/utf8/example_test.go
+++ b/src/unicode/utf8/example_test.go
@@ -214,3 +214,13 @@ func ExampleValidString() {
 	// true
 	// false
 }
+
+func ExampleAppendRune() {
+	buf1 := utf8.AppendRune(nil, 0x10000)
+	buf2 := utf8.AppendRune([]byte("init"), 0x10000)
+	fmt.Println(string(buf1))
+	fmt.Println(string(buf2))
+	// Output:
+	// 𐀀
+	// init𐀀
+}
diff --git a/src/unicode/utf8/utf8_test.go b/src/unicode/utf8/utf8_test.go
index a60040ecfd..e9be4d2d63 100644
--- a/src/unicode/utf8/utf8_test.go
+++ b/src/unicode/utf8/utf8_test.go
@@ -133,7 +133,7 @@ func TestAppendRune(t *testing.T) {
 			t.Errorf("AppendRune(nil, %#04x) = %s, want %s", m.r, buf, m.str)
 		}
 		if buf := AppendRune([]byte("init"), m.r); string(buf) != "init"+m.str {
-			t.Errorf("AppendRune(nil, %#04x) = %s, want %s", m.r, buf, "init"+m.str)
+			t.Errorf("AppendRune(init, %#04x) = %s, want %s", m.r, buf, "init"+m.str)
 		}
 	}
 }