Template string fails as destructuring default

Example:

https://buble.surge.sh/#const%20%5B%20fancyStr%20%3D%20%60%24%7Ba%7D%60%20%5D%20%3D%20something%3B%0Aconst%20%7B%20fancyStr2%20%3D%20%60%24%7Ba%7D%60%20%7D%20%3D%20somethingElse%3B%0A

Instead of compiling the template strings, Buble leaves the template strings as literals in the compiled result:

const [ fancyStr = `${a}` ] = something;
const { fancyStr2 = `${a}` } = somethingElse;

becomes

var fancyStr = something[0]; if ( fancyStr === void 0 ) fancyStr = `${a}`;
var fancyStr2 = somethingElse.fancyStr2; if ( fancyStr2 === void 0 ) fancyStr2 = `${a}`;

See the ${a} in both lines? That's the problem. Made Uglify choke. Didn't even notice it until then, because I've been testing in Chrome, and Chrome has template strings. I need IE 11, though, so I need these complied. Eventually, at least.