Fixes #17606

Change-Id: I040c7621cef265d44b58f16556e6d58660a2245d
Reviewed-on: https://go-review.googlesource.com/32889
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>