1 files changed, 4 insertions, 0 deletions
diff --git a/Lib/pydoc.py b/Lib/pydoc.py
index 376c4459fe..5edc77005a 100644
--- a/Lib/pydoc.py
+++ b/Lib/pydoc.py
@@ -2297,6 +2297,10 @@ def _start_server(urlhandler, port):
         def stop(self):
             """Stop the server and this thread nicely"""
             self.docserver.quit = True
+            self.join()
+            # explicitly break a reference cycle: DocServer.callback
+            # has indirectly a reference to ServerThread.
+            self.docserver = None
             self.serving = False
             self.url = None