diff --git a/cloudpickle/cloudpickle.py b/cloudpickle/cloudpickle.py
index 8211ab214..8dd5d816f 100644
--- a/cloudpickle/cloudpickle.py
+++ b/cloudpickle/cloudpickle.py
@@ -363,7 +363,10 @@ def save_function_tuple(self, func):
         save(_fill_function)  # skeleton function updater
         write(pickle.MARK)    # beginning of tuple that _fill_function expects
 
-        self._save_subimports(code, set(f_globals.values()) | set(closure))
+        self._save_subimports(
+            code,
+            itertools.chain(f_globals.values(), closure),
+        )
 
         # create a skeleton function object and memoize it
         save(_make_skel_func)
diff --git a/tests/cloudpickle_test.py b/tests/cloudpickle_test.py
index 28d1c2e70..43f8679f0 100644
--- a/tests/cloudpickle_test.py
+++ b/tests/cloudpickle_test.py
@@ -154,6 +154,18 @@ def g(n):
         g2 = pickle_depickle(f2(2))
         self.assertEqual(g2(5), 240)
 
+    def test_unhashable_closure(self):
+        def f():
+            s = set((1, 2))  # mutable set is unhashable
+
+            def g():
+                return len(s)
+
+            return g
+
+        g = pickle_depickle(f())
+        self.assertEqual(g(), 2)
+
     @pytest.mark.skipif(sys.version_info >= (3, 4)
                         and sys.version_info < (3, 4, 3),
                         reason="subprocess has a bug in 3.4.0 to 3.4.2")