diff --git a/django/db/models/query.py b/django/db/models/query.py
index 0f34fb8a5a..46a86fc03c 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -7,6 +7,8 @@ try:
 except NameError:
     from sets import Set as set     # Python 2.3 fallback
 
+from copy import deepcopy
+
 from django.db import connection, transaction, IntegrityError
 from django.db.models.aggregates import Aggregate
 from django.db.models.fields import DateField
@@ -40,6 +42,17 @@ class QuerySet(object):
     # PYTHON MAGIC METHODS #
     ########################
 
+    def __deepcopy__(self, memo):
+        """
+        Deep copy of a QuerySet doesn't populate the cache
+        """
+        obj_dict = deepcopy(self.__dict__, memo)
+        obj_dict['_iter'] = None
+
+        obj = self.__class__()
+        obj.__dict__.update(obj_dict)
+        return obj
+
     def __getstate__(self):
         """
         Allows the QuerySet to be pickled.
diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py
index 15b9fd6366..23f99e41ad 100644
--- a/django/db/models/sql/query.py
+++ b/django/db/models/sql/query.py
@@ -1625,10 +1625,14 @@ class BaseQuery(object):
                             entry.negate()
                             self.where.add(entry, AND)
                             break
-                elif not (lookup_type == 'in' and not value) and field.null:
+                elif not (lookup_type == 'in'
+                            and not hasattr(value, 'as_sql')
+                            and not hasattr(value, '_as_sql')
+                            and not value) and field.null:
                     # Leaky abstraction artifact: We have to specifically
                     # exclude the "foo__in=[]" case from this handling, because
                     # it's short-circuited in the Where class.
+                    # We also need to handle the case where a subquery is provided
                     entry = self.where_class()
                     entry.add((Constraint(alias, col, None), 'isnull', True), AND)
                     entry.negate()
diff --git a/tests/regressiontests/queries/models.py b/tests/regressiontests/queries/models.py
index b5fa377496..3649d27171 100644
--- a/tests/regressiontests/queries/models.py
+++ b/tests/regressiontests/queries/models.py
@@ -1143,6 +1143,33 @@ True
 >>> r.save()
 >>> Ranking.objects.all()
 [<Ranking: 3: a1>, <Ranking: 2: a2>, <Ranking: 1: a3>]
+
+# Regression test for #10742:
+# Queries used in an __in clause don't execute subqueries
+
+>>> subq = Author.objects.filter(num__lt=3000)
+>>> qs = Author.objects.filter(pk__in=subq)
+>>> list(qs)
+[<Author: a1>, <Author: a2>]
+# The subquery result cache should not be populated
+>>> subq._result_cache is None
+True
+
+>>> subq = Author.objects.filter(num__lt=3000)
+>>> qs = Author.objects.exclude(pk__in=subq)
+>>> list(qs)
+[<Author: a3>, <Author: a4>]
+# The subquery result cache should not be populated
+>>> subq._result_cache is None
+True
+
+>>> subq = Author.objects.filter(num__lt=3000)
+>>> list(Author.objects.filter(Q(pk__in=subq) & Q(name='a1')))
+[<Author: a1>]
+# The subquery result cache should not be populated
+>>> subq._result_cache is None
+True
+
 """}
 
 # In Python 2.3 and the Python 2.6 beta releases, exceptions raised in __len__