Problems with Datepicker and Select

[enterlight-metro]

I get the following warning:

[Vue warn]: method "lang" has already been defined as a prop.
found in
---> <VSelect> at /home/koala/projects/tusur/vue-strap/src/Select.vue

Same thing with Datepicker. I have not tried the other components. If I rename the lang prop to __lang, it works fine... Any ideas?

    "vue": {
      "version": "2.3.3",
      "resolved": "https://registry.npmjs.org/vue/-/vue-2.3.3.tgz",
      "integrity": "sha1-0eqo/eUkBzWkVj508sf+rZy7Bkw="
    },
    "vue-strap": {
      "version": "github:wffranco/vue-strap#7becab2b3f6e6b7e281afd777c455e3d83fde927",
      "requires": {
        "bootstrap": "3.3.7",
        "vue": "2.3.3",
        "vue-resource": "1.5.0",
        "vue-template-compiler": "2.3.3"
      }