diff --git a/itemloaders/utils.py b/itemloaders/utils.py
index 91a6556..4279b0f 100644
--- a/itemloaders/utils.py
+++ b/itemloaders/utils.py
@@ -20,7 +20,7 @@ def arg_to_iter(arg: Any) -> Iterable[Any]:
     """
     if arg is None:
         return []
-    if isinstance(arg, (list, tuple, Generator)):
+    if isinstance(arg, (list, tuple, set, Generator)):
         return arg
     return [arg]
 
diff --git a/tests/test_nested_items.py b/tests/test_nested_items.py
index fee9913..1536680 100644
--- a/tests/test_nested_items.py
+++ b/tests/test_nested_items.py
@@ -39,6 +39,13 @@ class TestItem:
     def test_dict(self):
         self._test_item({"foo": "bar"})
 
+    def test_set(self):
+        item = {"foo", "bar"}
+        il = ItemLoader()
+        il.add_value("item_list", item)
+
+        self.assertEqual(il.load_item(), {"item_list": ["foo", "bar"]})
+
     def test_scrapy_item(self):
         try:
             from scrapy import Field, Item