无法导入路径（未安装Config.Importer）

Question

When I use

import (
"go/types"
"go/importer"
)

conf := types.Config{
    Importer: importer.For("source", nil),
}
pkg, err := conf.Check(importSpec.Path.Value, fset, files, nil)

This errors on some machines saying

could not import path (Config.Importer not installed)

(see https://golang.org/src/go/types/resolver.go - line 155)

For my usecase I can't use the importer.Default().
Why is this failing on some machines? What can I do to get the source importer on all machines?