diff --git a/Lib/io.py b/Lib/io.py
index 072b756..67049e6 100644
--- a/Lib/io.py
+++ b/Lib/io.py
@@ -925,6 +925,11 @@
             raise StopIteration
         return line
 
+    @property
+    def encoding(self):
+        """Subclasses should override."""
+        return None
+
     # The following are provided for backwards compatibility
 
     def readlines(self, hint=None):
@@ -970,6 +975,10 @@
         self._snapshot = None
         self._seekable = self._telling = self.buffer.seekable()
 
+    @property
+    def encoding(self):
+        return self._encoding
+
     # A word about _snapshot.  This attribute is either None, or a
     # tuple (decoder_state, readahead, pending) where decoder_state is
     # the second (integer) item of the decoder state, readahead is the