diff --git a/modoboa/admin/templates/admin/quotas.html b/modoboa/admin/templates/admin/quotas.html
index 0c683aa42..132960a44 100644
--- a/modoboa/admin/templates/admin/quotas.html
+++ b/modoboa/admin/templates/admin/quotas.html
@@ -14,7 +14,8 @@
       <td>{{ mbox.get_quota }}M</td>
       <td>{{ mbox.quota }}M</td>
       <td name="quota">
-        <div id="quotabar" class="progress {% progress_color mbox.get_quota_in_percent %}">
+        <div id="quotabar" rel="tooltip" title="{{ mbox.get_quota_in_percent }}%"
+             class="progress {% progress_color mbox.get_quota_in_percent %}">
           <div class="bar" style="width: {{ mbox.get_quota_in_percent }}%"></div>
         </div>
       </td>
diff --git a/modoboa/admin/views.py b/modoboa/admin/views.py
index 99f680e07..bc04cfbe9 100644
--- a/modoboa/admin/views.py
+++ b/modoboa/admin/views.py
@@ -354,8 +354,10 @@ def list_quotas(request, tplname="admin/quotas.html"):
     if sort_order in ["address", "quota", "quota_value__bytes"]:
         mboxes = mboxes.order_by("%s%s" % (sort_dir, sort_order))
     elif sort_order == "quota_usage":
-        mboxes.select_related().extra(
-            select={'quota_usage': 'quota_value.bytes / (quota * 1048576) * 100'},
+        mboxes.extra(
+            select={'quota_usage': 'admin_quota.bytes / (admin_mailbox.quota * 1048576) * 100'},
+            where=["admin_quota.mbox_id=admin_mailbox.id"],
+            tables=["admin_quota"],
             order_by=["%s%s" % (sort_dir, sort_order)]
         )
     else: