diff --git a/cms/models.py b/cms/models.py
index 3e3ab68..010a047 100644
--- a/cms/models.py
+++ b/cms/models.py
@@ -5,7 +5,50 @@ from django.utils.translation import gettext_lazy as _
 
 from ckeditor.fields import RichTextField
 from embed_video.fields import EmbedVideoField
-from numberedmodel.models import NumberedModel
+
+# From https://github.com/JaapJoris/django-numberedmodel.git
+class NumberedModel(models.Model):
+    def number_with_respect_to(self):
+        return self.__class__.objects.all()
+
+    def _renumber(self):
+        '''Renumbers the queryset while preserving the instance's number'''
+
+        queryset = self.number_with_respect_to()
+        field_name = self.__class__._meta.ordering[-1].lstrip('-')
+        this_nr = getattr(self, field_name)
+        if this_nr is None:
+            this_nr = len(queryset) + 1
+
+        # The algorithm: loop over the queryset and set each object's
+        # number to the counter. When an object's number equals the
+        # number of this instance, set this instance's number to the
+        # counter, increment the counter by 1, and finish the loop
+        counter = 1
+        inserted = False
+        for other in queryset.exclude(pk=self.pk):
+            other_nr = getattr(other, field_name)
+            if counter >= this_nr and not inserted:
+                setattr(self, field_name, counter)
+                inserted = True
+                counter += 1
+            if other_nr != counter:
+                setattr(other, field_name, counter)
+                super(NumberedModel, other).save()
+            counter += 1
+        if not inserted:
+            setattr(self, field_name, counter)
+
+    def save(self, *args, **kwargs):
+        self._renumber()
+        super(NumberedModel, self).save(*args, **kwargs)
+
+    def delete(self, *args, **kwargs):
+        super(NumberedModel, self).delete(*args, **kwargs)
+        self._renumber()
+
+    class Meta:
+        abstract = True
 
 class Page(NumberedModel):
     position = models.PositiveIntegerField(_('position'), blank=True)