diff --git a/budget/models.py b/budget/models.py
index 0670d6e..3aac120 100644
--- a/budget/models.py
+++ b/budget/models.py
@@ -37,7 +37,7 @@ class Project(db.Model):
         # for each person
         for person in self.members:
             # get the list of bills he has to pay
-            bills = Bill.query.filter(Bill.owers.contains(person))
+            bills = Bill.query.options(orm.subqueryload(Bill.owers)).filter(Bill.owers.contains(person))
             for bill in bills.all():
                 if person != bill.payer:
                     share = bill.pay_each() * person.weight
diff --git a/budget/web.py b/budget/web.py
index 63fbe4d..87aef26 100644
--- a/budget/web.py
+++ b/budget/web.py
@@ -15,6 +15,7 @@ from flask.ext.mail import Mail, Message
 from flask.ext.babel import get_locale, gettext as _
 from smtplib import SMTPRecipientsRefused
 import werkzeug
+from sqlalchemy import orm
 
 # local modules
 from models import db, Project, Person, Bill
@@ -277,7 +278,8 @@ def list_bills():
     # set the last selected payer as default choice if exists
     if 'last_selected_payer' in session:
         bill_form.payer.data = session['last_selected_payer']
-    bills = g.project.get_bills()
+    # Preload the "owers" relationship for all bills
+    bills = g.project.get_bills().options(orm.subqueryload(Bill.owers))
 
     return render_template("list_bills.html",
             bills=bills, member_form=MemberForm(g.project),