diff --git a/xadmin/plugins/inline.py b/xadmin/plugins/inline.py
index 0592f7576..c95928553 100644
--- a/xadmin/plugins/inline.py
+++ b/xadmin/plugins/inline.py
@@ -227,10 +227,11 @@ def instance_form(self, **kwargs):
                 form.readonly_fields = []
                 inst = form.save(commit=False)
                 if inst:
+                    meta_field_names = [field.name for field in inst._meta.get_fields()]
                     for readonly_field in readonly_fields:
                         value = None
                         label = None
-                        if readonly_field in inst._meta.get_all_field_names():
+                        if readonly_field in meta_field_names:
                             label = inst._meta.get_field(readonly_field).verbose_name
                             value = smart_text(getattr(inst, readonly_field))
                         elif inspect.ismethod(getattr(inst, readonly_field, None)):