diff --git a/git/index/base.py b/git/index/base.py
@@ -8,7 +8,6 @@
import os
from stat import S_ISLNK
import subprocess
-import sys
import tempfile

from git.compat import (
@@ -18,7 +17,6 @@
    force_bytes,
    defenc,
    mviter,
-    is_win
)
from git.exc import (
    GitCommandError,
@@ -128,13 +126,7 @@ def _set_cache_(self, attr):
                    lfd.rollback()
            # END exception handling

-            # Here it comes: on windows in python 2.5, memory maps aren't closed properly
-            # Hence we are in trouble if we try to delete a file that is memory mapped,
-            # which happens during read-tree.
-            # In this case, we will just read the memory in directly.
-            # Its insanely bad ... I am disappointed !
-            allow_mmap = (is_win or sys.version_info[1] > 5)
-            stream = file_contents_ro(fd, stream=True, allow_mmap=allow_mmap)

            try:
                self._deserialize(stream)