diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py
index e27610178..f380435eb 100644
--- a/rest_framework/serializers.py
+++ b/rest_framework/serializers.py
@@ -220,6 +220,7 @@ class BaseSerializer(Field):
         return self.instance
 
     def is_valid(self, raise_exception=False):
+        assert self._initial_data is not None
         assert not hasattr(self, 'restore_object'), (
             'Serializer `%s.%s` has old-style version 2 `.restore_object()` '
             'that is no longer compatible with REST framework 3. '
diff --git a/tests/test_serializer.py b/tests/test_serializer.py
index f76cec9c3..25df987d4 100644
--- a/tests/test_serializer.py
+++ b/tests/test_serializer.py
@@ -95,6 +95,11 @@ class TestSerializer:
         serializer = self.Serializer()
         assert serializer.data == {'char': '', 'integer': None}
 
+    def test_empty_serializer_validity(self):
+        serializer = self.Serializer()
+        with pytest.raises(AssertionError):
+            serializer.is_valid()
+
     def test_missing_attribute_during_serialization(self):
         class MissingAttributes:
             pass