diff --git a/Lib/imaplib.py b/Lib/imaplib.py
index 1b37546..e020747 100644
--- a/Lib/imaplib.py
+++ b/Lib/imaplib.py
@@ -260,6 +260,7 @@
     def shutdown(self):
         """Close I/O established in "open"."""
         self.file.close()
+        self.sock.shutdown(socket.SHUT_RDWR)
         self.sock.close()