Fixes golang/go#19656

Change-Id: Ied20d3f25b6e147cc693a1dd1aeb9480adc6687e
Reviewed-on: https://go-review.googlesource.com/38405Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>