Fixes #19943

Change-Id: I5e0fefe44791d7b3556095d726c2a753ec551ef2
Reviewed-on: https://go-review.googlesource.com/c/147457
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>