django-imagekit: Error when trying to access width/height after url in templates

Error (see traceback below) occurs if you generate image with assignment tag and then access width or height after url. If you use width/height before url - everything goes fine. Also error disappears if you try to access already generated images.

All the related settings are the default ones.

Examples:

from django.template import Template, Context
tpl = "{% load imagekit %}{% generateimage 'spec_name' source=obj.photo as im %} {{ im.url }} {{ im.width }}"
Template(tpl).render(Context({'obj': obj}))  # error
# but no error for this:
tpl = "... {{ im.width }} {{ im.url }}"
# and also no error if thumb was already generated before render call

It’s quite strange and I’m not sure if that problem existed before because even in docs there’s an example that is doing exactly the same things.

Traceback:

.../lib/python3.4/site-packages/django/core/files/images.py in _get_width(self)
     16     """
     17     def _get_width(self):
---> 18         return self._get_image_dimensions()[0]
     19     width = property(_get_width)
     20

.../lib/python3.4/site-packages/django/core/files/images.py in _get_image_dimensions(self)
     26         if not hasattr(self, '_dimensions_cache'):
     27             close = self.closed
---> 28             self.open()
     29             self._dimensions_cache = get_image_dimensions(self, close=close)
     30         return self._dimensions_cache

.../lib/python3.4/site-packages/imagekit/files.py in open(self, mode)
     57     def open(self, mode='rb'):
     58         self._require_file()
---> 59         self.file.open(mode)
     60
     61     def _get_closed(self):

.../lib/python3.4/site-packages/django/core/files/base.py in open(self, mode)
    139             self.file = open(self.name, mode or self.mode)
    140         else:
--> 141             raise ValueError("The file cannot be reopened.")
    142
    143     def close(self):

PS. Confirmed for ImageKit 3.3 / Django 1.8-1.9 / Python 3.4.3