diff --git a/tests/basics/unary_op.py b/tests/basics/unary_op.py
index 3084c273e7..bd78a20d0d 100644
--- a/tests/basics/unary_op.py
+++ b/tests/basics/unary_op.py
@@ -15,3 +15,13 @@ print(not [])
 print(not [1,])
 print(not {})
 print(not {1:1})
+
+# check user instance
+class A: pass
+print(not A())
+
+# check user instances derived from builtins
+class B(int): pass
+print(not B())
+class C(list): pass
+print(not C())