diff --git a/netbox/extras/models/customfields.py b/netbox/extras/models/customfields.py
index e7e8d2b84..011afa42d 100644
--- a/netbox/extras/models/customfields.py
+++ b/netbox/extras/models/customfields.py
@@ -972,7 +972,7 @@ class CustomFieldChoiceSet(CloningMixin, ExportTemplatesMixin, OwnerMixin, Chang
         extra_choice_values = set()
 
         if self.base_choices:
-            valid_choice_values.update(CHOICE_SETS.get(self.base_choices).values())
+            valid_choice_values.update(value for value, _ in CHOICE_SETS.get(self.base_choices))
 
         if self.extra_choices:
             for value, _label in self.extra_choices:
@@ -1031,7 +1031,7 @@ class CustomFieldChoiceSet(CloningMixin, ExportTemplatesMixin, OwnerMixin, Chang
     def save(self, *args, **kwargs):
 
         # Sort choices if alphabetical ordering is enforced
-        if self.order_alphabetically:
+        if self.order_alphabetically and self.extra_choices:
             self.extra_choices = sorted(self.extra_choices, key=lambda x: x[0])
 
         return super().save(*args, **kwargs)
diff --git a/netbox/extras/tests/test_customfields.py b/netbox/extras/tests/test_customfields.py
index 8c695d382..c7c633991 100644
--- a/netbox/extras/tests/test_customfields.py
+++ b/netbox/extras/tests/test_customfields.py
@@ -466,6 +466,15 @@ class CustomFieldTestCase(TestCase):
 
         self.assertIn('choice_colors', cm.exception.message_dict)
 
+    @tag('regression')
+    def test_choice_set_with_base_choices_validates_without_error(self):
+        """Regression test for #22325: base-only choice sets must validate."""
+        for base in ('IATA', 'ISO_3166', 'UN_LOCODE'):
+            with self.subTest(base=base):
+                choice_set = CustomFieldChoiceSet(name=f'Test {base}', base_choices=base, order_alphabetically=True)
+                choice_set.full_clean()  # must not raise
+                choice_set.save()        # must not raise (extra_choices is None)
+
     def test_remove_selected_choice(self):
         """
         Removing a ChoiceSet choice that is referenced by an object should raise