From 23db935bcf258657682e66464bf8512def8af830 Mon Sep 17 00:00:00 2001
From: Zackery Spytz <zspytz@gmail.com>
Date: Fri, 29 Jun 2018 04:14:58 -0600
Subject: bpo-25862: Fix assertion failures in io.TextIOWrapper.tell().
 (GH-3918)

---
 Lib/_pyio.py | 1 +
 1 file changed, 1 insertion(+)

(limited to 'Lib/_pyio.py')

diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index c91a647a2f..f0d4f4ed27 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -2149,6 +2149,7 @@ class TextIOWrapper(TextIOBase):
         self.buffer.write(b)
         if self._line_buffering and (haslf or "\r" in s):
             self.flush()
+        self._set_decoded_chars('')
         self._snapshot = None
         if self._decoder:
             self._decoder.reset()
-- 
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