diff --git a/Lib/idlelib/run.py b/Lib/idlelib/run.py
index d10591246fd..88da23ba072 100644
--- a/Lib/idlelib/run.py
+++ b/Lib/idlelib/run.py
@@ -297,6 +297,11 @@ class MyHandler(rpc.RPCHandler):
         # page help() text to shell.
         import pydoc # import must be done here to capture i/o binding
         pydoc.pager = pydoc.plainpager
+
+        # Keep a reference to stdin so that it won't try to exit IDLE if
+        # sys.stdin gets changed from within IDLE's shell. See issue17838.
+        self._keep_stdin = sys.stdin
+
         self.interp = self.get_remote_proxy("interp")
         rpc.RPCHandler.getresponse(self, myseq=None, wait=0.05)
 
diff --git a/Misc/NEWS b/Misc/NEWS
index 10f00a466c1..c76a852f050 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -118,6 +118,8 @@ Library
 IDLE
 ----
 
+- Issue #17838: Allow sys.stdin to be reassigned.
+
 - Issue #14735: Update IDLE docs to omit "Control-z on Windows".
 
 - Issue #17585: Fixed IDLE regression. Now closes when using exit() or quit().