diff --git a/django/db/models/sql/expressions.py b/django/db/models/sql/expressions.py
index 920cbffe73..0914c2b3c1 100644
--- a/django/db/models/sql/expressions.py
+++ b/django/db/models/sql/expressions.py
@@ -66,7 +66,7 @@ class SQLEvaluator(object):
             else:
                 sql, params = '%s', (child,)
 
-            if hasattr(child, 'children') > 1:
+            if len(getattr(child, 'children', [])) > 1:
                 format = '(%s)'
             else:
                 format = '%s'
diff --git a/tests/modeltests/expressions/models.py b/tests/modeltests/expressions/models.py
index 27daabad71..b515682a9c 100644
--- a/tests/modeltests/expressions/models.py
+++ b/tests/modeltests/expressions/models.py
@@ -56,6 +56,16 @@ __test__ = {'API_TESTS': """
 >>> company_query
 [{'num_chairs': 2302, 'name': u'Example Inc.', 'num_employees': 2300}, {'num_chairs': 5, 'name': u'Foobar Ltd.', 'num_employees': 3}, {'num_chairs': 34, 'name': u'Test GmbH', 'num_employees': 32}]
 
+# Law of order of operations is followed
+>>> _ =company_query.update(num_chairs=F('num_employees') + 2 * F('num_employees'))
+>>> company_query
+[{'num_chairs': 6900, 'name': u'Example Inc.', 'num_employees': 2300}, {'num_chairs': 9, 'name': u'Foobar Ltd.', 'num_employees': 3}, {'num_chairs': 96, 'name': u'Test GmbH', 'num_employees': 32}]
+
+# Law of order of operations can be overridden by parentheses
+>>> _ =company_query.update(num_chairs=((F('num_employees') + 2) * F('num_employees')))
+>>> company_query
+[{'num_chairs': 5294600, 'name': u'Example Inc.', 'num_employees': 2300}, {'num_chairs': 15, 'name': u'Foobar Ltd.', 'num_employees': 3}, {'num_chairs': 1088, 'name': u'Test GmbH', 'num_employees': 32}]
+
 # The relation of a foreign key can become copied over to an other foreign key.
 >>> Company.objects.update(point_of_contact=F('ceo'))
 3