diff --git a/Lib/idlelib/run.py b/Lib/idlelib/run.py
index c66679cde92..5283a93b808 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 22e038b51e9..4c88a540647 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -294,6 +294,8 @@ C-API
 IDLE
 ----
 
+- Issue #17838: Allow sys.stdin to be reassigned.
+
 - Issue #13495: Avoid loading the color delegator twice in IDLE.
 
 - Issue #17798: Allow IDLE to edit new files when specified on command line.