diff --git a/nbformat/json_compat.py b/nbformat/json_compat.py
index 631e7182..9e472941 100644
--- a/nbformat/json_compat.py
+++ b/nbformat/json_compat.py
@@ -58,7 +58,7 @@ def validate(self, data):
 
     def iter_errors(self, data, schema=None):
         if schema is not None:
-            return self._default_validator.iter_errors(data, schema)
+            return super().iter_errors(data, schema)
 
         errors = []
         validate_func = self._validator
diff --git a/tests/test_validator.py b/tests/test_validator.py
index 46804a21..34ad06c9 100644
--- a/tests/test_validator.py
+++ b/tests/test_validator.py
@@ -201,7 +201,7 @@ def test_invalid_validator_raises_value_error_after_read():
         validate(nb)
 
 
-def test_fallback_validator_with_iter_errors_using_ref():
+def test_fallback_validator_with_iter_errors_using_ref(recwarn):
     """
     Test that when creating a standalone object (code_cell etc)
     the default validator is used as fallback.
@@ -211,6 +211,8 @@ def test_fallback_validator_with_iter_errors_using_ref():
     nbformat.v4.new_code_cell()
     nbformat.v4.new_markdown_cell()
     nbformat.v4.new_raw_cell()
+    assert len(recwarn) == 0
+
 
 
 def test_non_unique_cell_ids():