Gulp CSS minify & gzip + django-compressor not working

I am trying to minify and compress my css (and later js) and serve it up. To do this, I first minify and compress it with gulp and then serve the gzipped files with django-compressor (this will only make an HTTP request).

I pretty much followed this tutorial: http://www.revsys.com/blog/2014/oct/21/ultimate-front-end-development-setup/

Using gzipped files directly works well, however, when I try to group them with django-compressor, I get the following error:

UncompressableFileError at /
UnicodeDecodeError while processing '..../static/mincss/filename.min.css.gz' 
with charset utf-8-sig: 'utf8' codec 
can't decode byte 0x8b in position 1: invalid start byte

      

        
        
        
      

    

Which matches the compress on tag:

    {% compress css %}
      <link rel="stylesheet" href="{{ STATIC_URL }}mincss/filename.min.css.gz">
...more files
    {% endcompress %}

      

        
        
        
      

    

I'm 99% sure the generated gzipped files are correct. They are us-ascii (a subset of utf-8) and they contain a * .min.css file.

My respective settings (which I know) for the problem are the same as those given in the manual. The only difference is that in the manual it includes css files like this:

{% compress css %}
<link rel="stylesheet" href="{% static "stylesheets/main.css" %}" />
<link rel="stylesheet" href="{% static "stylesheets/some-other.css" %}" />
{% endcompress %}

      

        
        
        
      

    

But this way (although it works) doesn't use gzipped files, not even minified ones. What am I missing?