diff --git a/netbox/dcim/models.py b/netbox/dcim/models.py
index 0c587dd3d..b6ec28be2 100644
--- a/netbox/dcim/models.py
+++ b/netbox/dcim/models.py
@@ -187,7 +187,7 @@ class Rack(CreatedUpdatedModel):
 
         # Validate that Rack is tall enough to house the installed Devices
         if self.pk:
-            top_device = Device.objects.filter(rack=self).order_by('-position').first()
+            top_device = Device.objects.filter(rack=self).exclude(position__isnull=True).order_by('-position').first()
             if top_device:
                 min_height = top_device.position + top_device.device_type.u_height - 1
                 if self.u_height < min_height:
diff --git a/netbox/utilities/views.py b/netbox/utilities/views.py
index e1611a7ac..671390060 100644
--- a/netbox/utilities/views.py
+++ b/netbox/utilities/views.py
@@ -120,7 +120,7 @@ class ObjectEditView(View):
             'obj': obj,
             'obj_type': self.model._meta.verbose_name,
             'form': form,
-            'cancel_url': reverse(self.cancel_url) if self.cancel_url else obj.get_absolute_url(),
+            'cancel_url': obj.get_absolute_url() if obj else reverse(self.cancel_url),
         })
 
     def post(self, request, *args, **kwargs):
@@ -157,7 +157,7 @@ class ObjectEditView(View):
             'obj': obj,
             'obj_type': self.model._meta.verbose_name,
             'form': form,
-            'cancel_url': reverse(self.cancel_url) if self.cancel_url else obj.get_absolute_url(),
+            'cancel_url': obj.get_absolute_url() if obj else reverse(self.cancel_url),
         })