diff --git a/awx/api/views.py b/awx/api/views.py
index f493a9ae0d..cc7599db78 100644
--- a/awx/api/views.py
+++ b/awx/api/views.py
@@ -1686,6 +1686,15 @@ class InventoryDetail(RetrieveUpdateDestroyAPIView):
     model = Inventory
     serializer_class = InventoryDetailSerializer
 
+    def update(self, request, *args, **kwargs):
+        obj = self.get_object()
+        kind = self.request.data.get('kind') or kwargs.get('kind')
+
+        # Do not allow changes to an Inventory kind.
+        if kind is not None and obj.kind != kind:
+            return self.http_method_not_allowed(request, *args, **kwargs)
+        return super(InventoryDetail, self).update(request, *args, **kwargs)
+
     def destroy(self, request, *args, **kwargs):
         with ignore_inventory_computed_fields():
             with ignore_inventory_group_removal():
diff --git a/awx/main/fields.py b/awx/main/fields.py
index 25f4a85e66..a492932b43 100644
--- a/awx/main/fields.py
+++ b/awx/main/fields.py
@@ -331,8 +331,10 @@ class ImplicitRoleField(models.ForeignKey):
 
 class DynamicFilterField(models.TextField):
     def get_prep_value(self, value):
-        if value is None:
-            return value
+        # Change any false value to none.
+        # https://docs.python.org/2/library/stdtypes.html#truth-value-testing
+        if not value:
+            return None
         try:
             DynamicFilter().query_from_string(value)
         except RuntimeError, e:
diff --git a/awx/main/managers.py b/awx/main/managers.py
index 5884c88938..0969ad311a 100644
--- a/awx/main/managers.py
+++ b/awx/main/managers.py
@@ -27,9 +27,8 @@ class HostManager(models.Manager):
         set. Use the `host_filter` to generate the queryset for the hosts.
         """
         qs = super(HostManager, self).get_queryset()
-        if hasattr(self, 'instance') and self.instance is not None:
-            if hasattr(self.instance, 'kind') and self.instance.kind == 'dynamic':
-                if hasattr(self.instance, 'host_filter') and self.instance.host_filter is not None:
+        if hasattr(self, 'instance') and isinstance(self.instance, models.Inventory):
+            if self.instance.kind == 'dynamic' and self.instance.host_filter is not None:
                     q = DynamicFilter.query_from_string(self.instance.host_filter)
                     # If we are using host_filters, disable the core_filters, this allows
                     # us to access all of the available Host entries, not just the ones associated