diff --git a/paramiko/sftp_file.py b/paramiko/sftp_file.py
index 5050a21..1e5478b 100644
--- a/paramiko/sftp_file.py
+++ b/paramiko/sftp_file.py
@@ -122,10 +122,12 @@ class SFTPFile (BufferedFile):
         in the buffer, return None.  otherwise, behaves like a normal read.
         """
         # while not closed, and haven't fetched past the current position, and haven't reached EOF...
-        while not self._prefetch_done and not self._closed:
+        while True:
             offset = self._data_in_prefetch_buffers(self._realpos)
             if offset is not None:
                 break
+            if self._prefetch_done or self._closed:
+                break
             self.sftp._read_response()
             self._check_exception()
         if offset is None: