diff --git a/modoboa/lib/templatetags/lib_tags.py b/modoboa/lib/templatetags/lib_tags.py
index f6918bbd4..530c272bf 100644
--- a/modoboa/lib/templatetags/lib_tags.py
+++ b/modoboa/lib/templatetags/lib_tags.py
@@ -101,5 +101,10 @@ def extra_static_content(caller, st_type, user):
 @register.filter(name='localize_header_name')
 def localize_header_name(headername):
     """ Localizes the header names """
-    names = {"From": _("From"), "To": _("To"), "Date": _("Date"), "Subject": _("Subject")}
+    names = {
+        "From": _("From"),
+        "To": _("To"),
+        "Date": _("Date"),
+        "Subject": _("Subject")
+    }
     return names.get(headername, headername)
diff --git a/modoboa/limits/handlers.py b/modoboa/limits/handlers.py
index 9e7d8ef2f..aa793b955 100644
--- a/modoboa/limits/handlers.py
+++ b/modoboa/limits/handlers.py
@@ -220,9 +220,9 @@ def get_static_content(sender, caller, st_type, user, **kwargs):
         user.role in ["SuperAdmins", "SimpleUsers"]
     )
     if condition:
-        return []
+        return ""
     if st_type == "css":
-        return ["""<style>
+        return """<style>
 .resource {
     padding: 10px 15px;
 }
@@ -235,14 +235,14 @@ def get_static_content(sender, caller, st_type, user, **kwargs):
     color: #000000;
 }
 </style>
-"""]
-    return ["""
+"""
+    return """
 <script type="text/javascript">
 $(document).ready(function() {
     $(".progress").tooltip();
 });
 </script>
-"""]
+"""
 
 
 @receiver(admin_signals.extra_admin_content)
diff --git a/modoboa/relaydomains/handlers.py b/modoboa/relaydomains/handlers.py
index 54894ffcb..4a3032c9d 100644
--- a/modoboa/relaydomains/handlers.py
+++ b/modoboa/relaydomains/handlers.py
@@ -70,7 +70,7 @@ def extra_role_permissions(sender, role, **kwargs):
 def static_content(sender, caller, st_type, user, **kwargs):
     """Add extra static content."""
     if caller != "domains" or st_type != "js":
-        return []
+        return ""
 
     t = Template("""<script src="{{ STATIC_URL }}relaydomains/js/relay_domains.js" type="text/javascript"></script>
 <script type="text/javascript">
@@ -80,7 +80,7 @@ def static_content(sender, caller, st_type, user, **kwargs):
   });
 </script>
 """)
-    return [t.render(Context({"STATIC_URL": settings.STATIC_URL}))]
+    return t.render(Context({"STATIC_URL": settings.STATIC_URL}))
 
 
 @receiver(admin_signals.extra_domain_filters)
diff --git a/modoboa/urls.py b/modoboa/urls.py
index e01bc7268..9b246a232 100644
--- a/modoboa/urls.py
+++ b/modoboa/urls.py
@@ -25,7 +25,7 @@ urlpatterns += patterns(
 extra_routes = core_signals.extra_uprefs_routes.send(sender="urls")
 if extra_routes:
     extra_routes = reduce(
-        lambda a, b: a + b, [route for route in extra_routes])
+        lambda a, b: a + b, [route[1] for route in extra_routes])
     urlpatterns += patterns(
         '',
         *extra_routes