1 files changed, 1 insertions, 0 deletions
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()