Ghostblog 500 - Cannot read property 'includeZero' of undefined

I got this error when migrating my blog to Ghost 1.0. In order to make my theme compatible with Ghost 1.0 I would have to make some changes. After doing so I got the following error on one of my pages:

Ghostblog 500 - Cannot read property includeZero of undefined

I would like to make a disclaimer here. I have very little experience with handlebars (I have not worked with it for years). But it seemed that I had made a mistake.

The error was that I had written the following:

{{#if img_url feature_image}}

Instead of just this:

{{#if feature_image}}

I hope this helps someone out there :)