1 files changed, 4 insertions, 0 deletions
diff --git a/Lib/copyreg.py b/Lib/copyreg.py
index 356db6f083e..c8a52a2dc63 100644
--- a/Lib/copyreg.py
+++ b/Lib/copyreg.py
@@ -89,6 +89,10 @@ def _reduce_ex(self, proto):
         except AttributeError:
             dict = None
     else:
+        if (type(self).__getstate__ is object.__getstate__ and
+            getattr(self, "__slots__", None)):
+            raise TypeError("a class that defines __slots__ without "
+                            "defining __getstate__ cannot be pickled")
         dict = getstate()
     if dict:
         return _reconstructor, args, dict