diff --git a/shop/epay.py b/shop/epay.py
index 50be8a8f..d7df0822 100644
--- a/shop/epay.py
+++ b/shop/epay.py
@@ -4,7 +4,7 @@ from django.conf import settings
 def calculate_epay_hash(order, request):
     hashstring = (
         '{merchant_number}{description}11{amount}DKK'
-        '{order_id}{accept_url}{cancel_url}{md5_secret}'
+        '{order_id}{accept_url}{cancel_url}{callback_url}{md5_secret}'
     ).format(
         merchant_number=settings.EPAY_MERCHANT_NUMBER,
         description=order.description,
@@ -12,6 +12,7 @@ def calculate_epay_hash(order, request):
         order_id=order.pk,
         accept_url = order.get_epay_accept_url(request),
         cancel_url = order.get_cancel_url(request),
+        callback_url = order.get_epay_callback_url(request),
         md5_secret=settings.EPAY_MD5_SECRET,
     )
     epay_hash = hashlib.md5(hashstring).hexdigest()