diff --git a/django_mongodb_engine/compiler.py b/django_mongodb_engine/compiler.py
index 542bb389..e5b4db3f 100644
--- a/django_mongodb_engine/compiler.py
+++ b/django_mongodb_engine/compiler.py
@@ -239,9 +239,12 @@ def add_filters(self, filters, query=None):
                             else:
                                 existing.update(lookup)
                         else:
-                            # {'$gt': o1} + {'$lt': o2} --> {'$gt': o1, '$lt': o2}
-                            assert all(key not in existing for key in lookup.keys()), [lookup, existing]
-                            existing.update(lookup)
+                            if '$in' in lookup and '$in' in existing:
+                                existing['$in'] = list(set(lookup['$in'] + existing['$in']))
+                            else:
+                                # {'$gt': o1} + {'$lt': o2} --> {'$gt': o1, '$lt': o2}
+                                assert all(key not in existing for key in lookup.keys()), [lookup, existing]
+                                existing.update(lookup)
                     else:
                         key = '$nin' if self._negated else '$all'
                         existing.setdefault(key, []).append(lookup)
diff --git a/tests/query/tests.py b/tests/query/tests.py
index e9d0741c..9ac366ab 100644
--- a/tests/query/tests.py
+++ b/tests/query/tests.py
@@ -234,6 +234,13 @@ def test_multiple_filter_on_same_name(self):
             []
         )
 
+        # Tests chaining on primary keys
+        blog_id = Blog.objects.get().id
+        self.assertEqual(
+            Blog.objects.filter(pk = blog_id).filter(pk = blog_id).get(),
+            Blog.objects.get()
+        )
+
     def test_negated_Q(self):
         blogs = [Blog.objects.create(title=title) for title in
                  ('blog', 'other blog', 'another blog')]