Fixes #24864

Change-Id: Iaffd23b368aff663bfc09a4e6277c01e7b5ea48d
GitHub-Last-Rev: 98e39b7bff6e646d48c0bf961aee0075a9034ab2
GitHub-Pull-Request: golang/go#24865
Reviewed-on: https://go-review.googlesource.com/106986Reviewed-by: Giovanni Bajo <rasky@develer.com>
Reviewed-by: Rob Pike <r@golang.org>