ES6 lost "this" scope when method is assigned to a variable

lost-scope.js

class Foo {
  static bar() {
   return 'bar'; 
  }
  
  baz() {
   return this.constructor.bar(); 
  }
}

const foo = new Foo();

foo.baz(); // works fine

const baz = foo.baz;

baz(); // TypeError: Cannot read property 'constructor' of undefined