diff --git a/odoo/addons/base/models/ir_model.py b/odoo/addons/base/models/ir_model.py
index ab413a764d4..06647266004 100644
--- a/odoo/addons/base/models/ir_model.py
+++ b/odoo/addons/base/models/ir_model.py
@@ -1381,8 +1381,15 @@ class IrModelSelection(models.Model):
             if not field or not field.store or Model._abstract:
                 continue
 
-            ondelete = (field.ondelete or {}).get(selection.value) or 'set null'
-            if callable(ondelete):
+            ondelete = (field.ondelete or {}).get(selection.value)
+            # special case for custom fields
+            if ondelete is None and field.manual and not field.required:
+                ondelete = 'set null'
+
+            if ondelete is None:
+                # nothing to do, the selection does not come from a field extension
+                continue
+            elif callable(ondelete):
                 ondelete(selection._get_records())
             elif ondelete == 'set null':
                 selection._get_records().write({field.name: False})
diff --git a/odoo/addons/test_new_api/tests/test_new_fields.py b/odoo/addons/test_new_api/tests/test_new_fields.py
index 3e85a0aa314..ff60190704d 100644
--- a/odoo/addons/test_new_api/tests/test_new_fields.py
+++ b/odoo/addons/test_new_api/tests/test_new_fields.py
@@ -3056,6 +3056,16 @@ class TestSelectionOndelete(common.TransactionCase):
 
         self.assertFalse(rec.my_selection)
 
+    def test_required_base_selection_field(self):
+        # test that no ondelete action is executed on a required selection field that is not
+        # extended, only required fields that extend it with selection_add should
+        # have ondelete actions defined
+        rec = self.env[self.MODEL_REQUIRED].create({'my_selection': 'foo'})
+        self.assertEqual(rec.my_selection, 'foo')
+
+        self._unlink_option(self.MODEL_REQUIRED, 'foo')
+        self.assertEqual(rec.my_selection, 'foo')
+
 
 @common.tagged('selection_ondelete_advanced')
 class TestSelectionOndeleteAdvanced(common.TransactionCase):