diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index 4a3405f3f0..e9e3f4a0a3 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -196,7 +196,7 @@ class Field(object):
             return
         if self._choices and value:
             for option_key, option_value in self.choices:
-                if type(option_value) in (tuple, list):
+                if isinstance(option_value, (list, tuple)):
                     # This is an optgroup, so look inside the group for options.
                     for optgroup_key, optgroup_value in option_value:
                         if value == optgroup_key:
@@ -431,7 +431,7 @@ 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 dd5ae1e427..6d0fdea26e 100644
--- a/django/forms/fields.py
+++ b/django/forms/fields.py
@@ -621,7 +621,7 @@ 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):