What version of Go are you using (go version)?

go version go1.16.3 darwin/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

GOHOSTARCH="amd64"
GOHOSTOS="darwin"

What did you do?

Run go generate . on a module with only the following file:

package translations

//go:generate gotext -srclang=en update -out=catalog.go -lang=en,nl .

import (
	"golang.org/x/text/message"
)

func dummyMessages(p *message.Printer) {
	p.Printf("/b")
	p.Printf("/")
	p.Printf("/a")
}

What did you expect to see?

The string / to appear in locales/en/out.gotext.json

What did you see instead?

Only the strings /b and /a.