diff --git a/src/sage/combinat/subset.py b/src/sage/combinat/subset.py
index 5fea2f5f97b..6c8d923ce9f 100644
--- a/src/sage/combinat/subset.py
+++ b/src/sage/combinat/subset.py
@@ -321,8 +321,10 @@ def __contains__(self, value):
             True
             sage: 2 in S
             False
+            sage: {1, 2} in S
+            True
         """
-        if value not in Sets():
+        if value not in Sets() and not isinstance(value, (set, frozenset)):
             return False
         return all(v in self._s for v in value)