2.2.10: 'import' and 'export' may appear only with 'sourceType: module'

[goldfire]

Since upgrading to 2.2.10, I'm getting the following error when trying to rollup. Switching back one version makes everything work as expected. I'm not completely clear on what this error is referring to, any ideas?

Error transforming /path/to/src/components/App.vue with 'vue' plugin: 'import' and 'export' may appear only with 'sourceType: module' (9:2)
SyntaxError: Error transforming /path/to/src/components/App.vue with 'vue' plugin: 'import' and 'export' may appear only with 'sourceType: module' (9:2)
5 :
6 :
7 :
8 :
9 :   import Toolbar from './Toolbar.vue';
      ^
    at Parser.pp$4.raise (/path/to/node_modules/vue-template-es2015-compiler/buble.js:2231:15)
    at Parser.pp$1.parseStatement (/path/to/node_modules/vue-template-es2015-compiler/buble.js:727:16)
    at Parser.pp$1.parseTopLevel (/path/to/node_modules/vue-template-es2015-compiler/buble.js:648:25)
    at Parser.parse (/path/to/node_modules/vue-template-es2015-compiler/buble.js:526:17)
    at parse (/path/to/node_modules/vue-template-es2015-compiler/buble.js:3108:39)
    at Object.transform (/path/to/node_modules/vue-template-es2015-compiler/buble.js:11969:9)
    at transpile (/path/to/node_modules/vue-template-es2015-compiler/index.js:17:20)
    at injectRender (/path/to/node_modules/rollup-plugin-vue/dist/rollup-plugin-vue.common.js:82:20)
    at processScript (/path/to/node_modules/rollup-plugin-vue/dist/rollup-plugin-vue.common.js:168:18)
    at vueTransform (/path/to/node_modules/rollup-plugin-vue/dist/rollup-plugin-vue.common.js:206:14)