diff -r fee3dd2c5b7e Lib/idlelib/PyShell.py
--- a/Lib/idlelib/PyShell.py	Tue Dec 24 09:02:24 2013 +0200
+++ b/Lib/idlelib/PyShell.py	Tue Dec 24 09:41:39 2013 +0200
@@ -1384,6 +1384,9 @@
         line = self._line_buffer or self.shell.readline()
         if size < 0:
             size = len(line)
+        eol = line.find('\n', 0, size)
+        if eol >= 0:
+            size = eol + 1
         self._line_buffer = line[size:]
         return line[:size]