diff --git a/netbox/dcim/forms.py b/netbox/dcim/forms.py
index 930ac166b..ec293b7e1 100644
--- a/netbox/dcim/forms.py
+++ b/netbox/dcim/forms.py
@@ -27,6 +27,7 @@ from utilities.forms import (
     NumericArrayField, SelectWithPK, SmallTextarea, SlugField, StaticSelect2, StaticSelect2Multiple, TagFilterField,
     BOOLEAN_WITH_BLANK_CHOICES,
 )
+from utilities.utils import union_list
 from virtualization.models import Cluster, ClusterGroup
 from .choices import *
 from .constants import *
@@ -1910,6 +1911,18 @@ class DeviceForm(BootstrapMixin, TenancyForm, CustomFieldModelForm):
             elif self.initial.get('rack') and str(self.initial.get('face')):
                 position_choices = Rack.objects.get(pk=self.initial['rack']) \
                     .get_rack_units(face=self.initial.get('face'), exclude=pk)
+            elif self.is_bound and self.data.get('rack'):
+                front = Rack.objects.get(pk=self.data['rack']) \
+                    .get_rack_units(face=DeviceFaceChoices.FACE_FRONT, exclude=pk)
+                rear = Rack.objects.get(pk=self.data['rack']) \
+                    .get_rack_units(face=DeviceFaceChoices.FACE_REAR, exclude=pk)
+                position_choices = union_list(front, rear, 'name')
+            elif self.initial.get('rack'):
+                front = Rack.objects.get(pk=self.initial['rack']) \
+                    .get_rack_units(face=DeviceFaceChoices.FACE_FRONT, exclude=pk)
+                rear = Rack.objects.get(pk=self.initial['rack']) \
+                    .get_rack_units(face=DeviceFaceChoices.FACE_REAR, exclude=pk)
+                position_choices = union_list(front, rear, 'name')
             else:
                 position_choices = []
         except Rack.DoesNotExist:
diff --git a/netbox/utilities/utils.py b/netbox/utilities/utils.py
index d76b469b2..512fe4e78 100644
--- a/netbox/utilities/utils.py
+++ b/netbox/utilities/utils.py
@@ -83,6 +83,30 @@ def count_related(model, field):
     return Coalesce(subquery, 0)
 
 
+def intersect_list(llist, rlist, key):
+    result = []
+    for left in llist:
+        for right in rlist:
+            if isinstance(left, dict) and isinstance(right, dict) and key in left.keys() and key in right.keys() and \
+                    left[key] == right[key]:
+                result.append(left)
+                break
+    return result
+
+
+def union_list(llist, rlist, key):
+    result = llist
+    for right in rlist:
+        found = False
+        for left in llist:
+            if isinstance(left, dict) and isinstance(right, dict) and key in left.keys() and key in right.keys() and \
+                    left[key] == right[key]:
+                found = True
+        if found is False:
+            result.append(right)
+    return result
+
+
 def serialize_object(obj, extra=None, exclude=None):
     """
     Return a generic JSON representation of an object using Django's built-in serializer. (This is used for things like