diff --git a/polymorphic/query.py b/polymorphic/query.py
index ead4fca..b776f55 100644
--- a/polymorphic/query.py
+++ b/polymorphic/query.py
@@ -112,9 +112,9 @@ class PolymorphicQuerySet(QuerySet):
 
     def _filter_or_exclude(self, negate, *args, **kwargs):
         "We override this internal Django functon as it is used for all filter member functions."
-        translate_polymorphic_filter_definitions_in_args(self.model, args, using=self._db)  # the Q objects
+        q_objects = translate_polymorphic_filter_definitions_in_args(self.model, args, using=self._db)  # the Q objects
         additional_args = translate_polymorphic_filter_definitions_in_kwargs(self.model, kwargs, using=self._db)  # filter_field='data'
-        return super(PolymorphicQuerySet, self)._filter_or_exclude(negate, *(list(args) + additional_args), **kwargs)
+        return super(PolymorphicQuerySet, self)._filter_or_exclude(negate, *(list(q_objects) + additional_args), **kwargs)
 
     def order_by(self, *args, **kwargs):
         """translate the field paths in the args, then call vanilla order_by."""
@@ -472,3 +472,4 @@ class PolymorphicQuerySet(QuerySet):
             return olist
         clist = PolymorphicQuerySet._p_list_class(olist)
         return clist
+
diff --git a/polymorphic/query_translate.py b/polymorphic/query_translate.py
index b7a53e9..666ca75 100644
--- a/polymorphic/query_translate.py
+++ b/polymorphic/query_translate.py
@@ -93,17 +93,15 @@ def translate_polymorphic_filter_definitions_in_args(queryset_model, args, using
     """
     Translate the non-keyword argument list for PolymorphicQuerySet.filter()
 
-    In the args list, we replace all kwargs to Q-objects that contain special
+    In the args list, we return all kwargs to Q-objects that contain special
     polymorphic functionality with their vanilla django equivalents.
     We traverse the Q object tree for this (which is simple).
 
-    TODO: investigate: we modify the Q-objects ina args in-place. Is this OK?
 
-    Modifies: args list
+    Returns: modified Q objects
     """
+    return [translate_polymorphic_Q_object(queryset_model, q.clone(), using=using) for q in args]
 
-    for q in args:
-        translate_polymorphic_Q_object(queryset_model, q, using=using)
 
 
 def _translate_polymorphic_filter_definition(queryset_model, field_path, field_val, using=DEFAULT_DB_ALIAS):
@@ -266,3 +264,4 @@ def _create_model_filter_Q(modellist, not_instance_of=False, using=DEFAULT_DB_AL
     if not_instance_of:
         q_ored = ~q_ored
     return q_ored
+
diff --git a/polymorphic/tests.py b/polymorphic/tests.py
index ca11733..92fe132 100644
--- a/polymorphic/tests.py
+++ b/polymorphic/tests.py
@@ -824,6 +824,23 @@ class PolymorphicTests(TestCase):
         self.assertEqual(repr(objects[0]), '<Model2B: id 2, field1 (CharField), field2 (CharField)>')
         self.assertEqual(repr(objects[1]), '<Model2C: id 3, field1 (CharField), field2 (CharField), field3 (CharField)>')
 
+    def test_query_filter_exclude_is_immutable(self):
+        # given
+        q_to_reuse = Q(Model2B___field2='something')
+        untouched_q_object = Q(Model2B___field2='something')
+        # when
+        Model2A.objects.filter(q_to_reuse).all()
+        # then
+        self.assertEquals(q_to_reuse.children, untouched_q_object.children)
+
+        # given
+        q_to_reuse = Q(Model2B___field2='something')
+        untouched_q_object = Q(Model2B___field2='something')
+        # when
+        Model2B.objects.filter(q_to_reuse).all()
+        # then
+        self.assertEquals(q_to_reuse.children, untouched_q_object.children)
+
     def test_polymorphic___filter_field(self):
         p = ModelUnderRelParent.objects.create(_private=True, field1='AA')
         ModelUnderRelChild.objects.create(parent=p, _private2=True)
@@ -1224,3 +1241,4 @@ class RegressionTests(TestCase):
 
         expected_queryset = [bottom]
         self.assertQuerysetEqual(Bottom.objects.all(), [repr(r) for r in expected_queryset])
+