diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index 2a7c17f876..d3eee8aeb6 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -304,7 +304,7 @@ class Field(object):
         """Flattened version of choices tuple."""
         flat = []
         for choice, value in self.choices:
-            if type(value) in (list, tuple):
+            if isinstance(value, (list, tuple)):
                 flat.extend(value)
             else:
                 flat.append((choice,value))
diff --git a/django/forms/fields.py b/django/forms/fields.py
index 581d32d923..18174360f6 100644
--- a/django/forms/fields.py
+++ b/django/forms/fields.py
@@ -660,7 +660,7 @@ class ChoiceField(Field):
     def valid_value(self, value):
         "Check to see if the provided value is a valid choice"
         for k, v in self.choices:
-            if type(v) in (tuple, list):
+            if isinstance(v, (list, tuple)):
                 # This is an optgroup, so look inside the group for options
                 for k2, v2 in v:
                     if value == smart_unicode(k2):