diff --git a/Lib/fileinput.py b/Lib/fileinput.py
index c1b0ec9..166c631 100644
--- a/Lib/fileinput.py
+++ b/Lib/fileinput.py
@@ -209,15 +209,10 @@
         self._isstdin = False
         self._backupfilename = None
         # restrict mode argument to reading modes
-        if mode not in ('r', 'rU', 'U', 'rb'):
-            raise ValueError("FileInput opening mode must be one of "
-                             "'r', 'rU', 'U' and 'rb'")
-        if 'U' in mode:
-            import warnings
-            warnings.warn("'U' mode is deprecated",
-                          DeprecationWarning, 2)
+        if mode not in ('r', 'rb'):
+            raise ValueError("FileInput opening mode must be 'r' or 'rb'")
         self._mode = mode
-        self._write_mode = mode.replace('r', 'w') if 'U' not in mode else 'w'
+        self._write_mode = mode.replace('r', 'w')
         if openhook:
             if inplace:
                 raise ValueError("FileInput cannot use an opening hook in inplace mode")