1 files changed, 6 insertions, 0 deletions
diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index 74047bf475b..265edab1134 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -944,6 +944,12 @@ class BufferedReader(_BufferedIOMixin):
         # Special case for when the number of bytes to read is unspecified.
         if n is None or n == -1:
             self._reset_read_buf()
+            if hasattr(self.raw, 'readall'):
+                chunk = self.raw.readall()
+                if chunk is None:
+                    return buf[pos:] or None
+                else:
+                    return buf[pos:] + chunk
             chunks = [buf[pos:]]  # Strip the consumed bytes.
             current_size = 0
             while True: