diff --git a/multidict/_multidict_py.py b/multidict/_multidict_py.py
index f9c8f384a..bff82767a 100644
--- a/multidict/_multidict_py.py
+++ b/multidict/_multidict_py.py
@@ -185,12 +185,13 @@ def _extend(self, args, kwargs, name, method):
             elif hasattr(arg, 'items'):
                 items = arg.items()
             else:
+                items = []
                 for item in arg:
                     if not len(item) == 2:
                         raise TypeError(
                             "{} takes either dict or list of (key, value) "
                             "tuples".format(name))
-                items = arg
+                    items.append(item)
 
             for key, value in items:
                 method(key, value)
diff --git a/tests/test_multidict.py b/tests/test_multidict.py
index 8fa6e785e..268a26e95 100644
--- a/tests/test_multidict.py
+++ b/tests/test_multidict.py
@@ -73,6 +73,15 @@ def test_instantiate__with_kwargs(self):
         self.assertEqual(sorted(d.items()), [('key', 'value1'),
                                              ('key2', 'value2')])
 
+    def test_instantiate__from_generator(self):
+        d = self.make_dict((str(i), i) for i in range(2))
+
+        self.assertEqual(d, {'0': 0, '1': 1})
+        self.assertEqual(len(d), 2)
+        self.assertEqual(sorted(d.keys()), ['0', '1'])
+        self.assertEqual(sorted(d.values()), [0, 1])
+        self.assertEqual(sorted(d.items()), [('0', 0), ('1', 1)])
+
     def test_getone(self):
         d = self.make_dict([('key', 'value1')], key='value2')
         self.assertEqual(d.getone('key'), 'value1')