Ember.js use link-to helper in custom helper

I'm using ember-cli and getting an exception when trying to use a helper within a helper.

The following line ...

return Ember.Handlebars.helpers['link-to'](this, args);

Causes the exception ...

Uncaught TypeError: Ember.default.Handlebars.helpers.link-to.apply is not a function

Also I was trying to use the following elsewhere in the code and got a similar error, is the cause the same?

Ember.Handlebars.helpers.view.call(this, MyView, options);

Exception ...

Uncaught TypeError: Ember.default.Handlebars.helpers.view.call is not a function