diff --git a/rhodecode/lib/celerylib/tasks.py b/rhodecode/lib/celerylib/tasks.py
--- a/rhodecode/lib/celerylib/tasks.py
+++ b/rhodecode/lib/celerylib/tasks.py
@@ -8,10 +8,15 @@ from rhodecode.lib.smtp_mailer import Sm
 from rhodecode.lib.utils import OrderedDict
 from time import mktime
 from vcs.backends.hg import MercurialRepository
-import json
 import traceback
 
 try:
+    import json
+except ImportError:
+    #python 2.5 compatibility
+    import simplejson as json
+
+try:
     from celeryconfig import PYLONS_CONFIG as config
     celery_on = True
 except ImportError: