diff --git a/jinja2/bccache.py b/jinja2/bccache.py

index 09ff845..c31a905 100644

--- a/jinja2/bccache.py

+++ b/jinja2/bccache.py

@@ -16,6 +16,7 @@

 """

 from os import path, listdir

 import os

+import stat

 import sys

 import errno

 import marshal

@@ -230,6 +231,14 @@ class FileSystemBytecodeCache(BytecodeCache):

             if e.errno != errno.EEXIST:

                 raise

+        if os.lstat(actual_dir).st_uid != os.getuid():

+            raise RuntimeError('Someone else owns temp directory with your '

+                               'uid. You need to explicitly provide another.')

+

+        if stat.S_IMODE(os.lstat(actual_dir).st_mode) != 448:

+            raise RuntimeError('Bad permission flags on temp directory, '

+                               'shoud be 0700. You need to fix this.')

+

         return actual_dir

     def _get_cache_filename(self, bucket):