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):