diff --git a/model_utils/managers.py b/model_utils/managers.py
index 2f2d1d2..98a2a54 100644
--- a/model_utils/managers.py
+++ b/model_utils/managers.py
@@ -48,11 +48,10 @@ class InheritanceIterable(ModelIterable):
 class InheritanceQuerySetMixin(object):
     def __init__(self, *args, **kwargs):
         super(InheritanceQuerySetMixin, self).__init__(*args, **kwargs)
-        if django.VERSION > (1, 8):
-            self._iterable_class = InheritanceIterable
+        self._iterable_class = InheritanceIterable
 
     def select_subclasses(self, *subclasses):
-        levels = self._get_maximum_depth()
+        levels = None
         calculated_subclasses = self._get_subclasses_recurse(
             self.model, levels=levels)
         # if none were passed in, we can just short circuit and select all
@@ -151,12 +150,9 @@ class InheritanceQuerySetMixin(object):
         recursively, returning a `list` of strings representing the
         relations for select_related
         """
-        if django.VERSION < (1, 8):
-            related_objects = model._meta.get_all_related_objects()
-        else:
-            related_objects = [
-                f for f in model._meta.get_fields()
-                if isinstance(f, OneToOneRel)]
+        related_objects = [
+            f for f in model._meta.get_fields()
+            if isinstance(f, OneToOneRel)]
 
         rels = [
             rel for rel in related_objects
@@ -199,10 +195,7 @@ class InheritanceQuerySetMixin(object):
                 related = parent_link.remote_field
             ancestry.insert(0, related.get_accessor_name())
             if levels or levels is None:
-                if django.VERSION < (1, 8):
-                    parent_model = related.parent_model
-                else:
-                    parent_model = related.model
+                parent_model = related.model
                 parent_link = parent_model._meta.get_ancestor_link(
                     self.model)
             else:
@@ -230,17 +223,6 @@ class InheritanceQuerySetMixin(object):
     def get_subclass(self, *args, **kwargs):
         return self.select_subclasses().get(*args, **kwargs)
 
-    def _get_maximum_depth(self):
-        """
-        Under Django versions < 1.6, to avoid triggering
-        https://code.djangoproject.com/ticket/16572 we can only look
-        as far as children.
-        """
-        levels = None
-        if django.VERSION < (1, 6, 0):
-            levels = 1
-        return levels
-
 
 class InheritanceQuerySet(InheritanceQuerySetMixin, QuerySet):
     pass
diff --git a/model_utils/tracker.py b/model_utils/tracker.py
index 93e4a5d..0fec85d 100644
--- a/model_utils/tracker.py
+++ b/model_utils/tracker.py
@@ -97,35 +97,19 @@ class FieldInstanceTracker(object):
             def _get_field_name(self):
                 return self.field.name
 
-        if django.VERSION >= (1, 8):
-            self.instance._deferred_fields = self.instance.get_deferred_fields()
-            for field in self.instance._deferred_fields:
-                if django.VERSION >= (1, 10):
-                    field_obj = getattr(self.instance.__class__, field)
-                else:
-                    field_obj = self.instance.__class__.__dict__.get(field)
-                if isinstance(field_obj, FileDescriptor):
-                    field_tracker = FileDescriptorTracker(field_obj.field)
-                    setattr(self.instance.__class__, field, field_tracker)
-                else:
-                    field_tracker = DeferredAttributeTracker(
-                        field_obj.field_name, None)
-                    setattr(self.instance.__class__, field, field_tracker)
-        else:
-            for field in self.fields:
+        self.instance._deferred_fields = self.instance.get_deferred_fields()
+        for field in self.instance._deferred_fields:
+            if django.VERSION >= (1, 10):
+                field_obj = getattr(self.instance.__class__, field)
+            else:
                 field_obj = self.instance.__class__.__dict__.get(field)
-                if isinstance(field_obj, DeferredAttribute):
-                    self.instance._deferred_fields.add(field)
-
-                    # Django 1.4
-                    if django.VERSION >= (1, 5):
-                        model = None
-                    else:
-                        model = field_obj.model_ref()
-
-                    field_tracker = DeferredAttributeTracker(
-                        field_obj.field_name, model)
-                    setattr(self.instance.__class__, field, field_tracker)
+            if isinstance(field_obj, FileDescriptor):
+                field_tracker = FileDescriptorTracker(field_obj.field)
+                setattr(self.instance.__class__, field, field_tracker)
+            else:
+                field_tracker = DeferredAttributeTracker(
+                    field_obj.field_name, None)
+                setattr(self.instance.__class__, field, field_tracker)
 
 
 class FieldTracker(object):
diff --git a/tests/test_managers/test_inheritance_manager.py b/tests/test_managers/test_inheritance_manager.py
index 4509175..39c694e 100644
--- a/tests/test_managers/test_inheritance_manager.py
+++ b/tests/test_managers/test_inheritance_manager.py
@@ -115,9 +115,6 @@ class InheritanceManagerTests(TestCase):
                 "inheritancemanagertestchild2").get(pk=self.child1.pk)
             obj.inheritancemanagertestchild1
 
-    def test_version_determining_any_depth(self):
-        self.assertIsNone(self.get_manager().all()._get_maximum_depth())
-
     def test_manually_specifying_parent_fk_including_grandchildren(self):
         """
         given a Model which inherits from another Model, but also declares