diff -r ddc4d837a0b7 Lib/bdb.py
--- a/Lib/bdb.py        Sat Apr 16 09:29:17 2016 +0000
+++ b/Lib/bdb.py        Sat Apr 16 05:04:09 2016 -0700
@@ -260,6 +260,7 @@
             while frame and frame is not self.botframe:
                 del frame.f_trace
                 frame = frame.f_back
+            self.trace_dispatch = None

     def set_quit(self):
         self.stopframe = self.botframe