diff --git a/src/pretix/helpers/urls.py b/src/pretix/helpers/urls.py
index ec9087f452..79262df390 100644
--- a/src/pretix/helpers/urls.py
+++ b/src/pretix/helpers/urls.py
@@ -1,5 +1,9 @@
+from urllib.parse import urljoin
 from django.conf import settings
+from django.core.urlresolvers import reverse
 
 
-def build_absolute_uri(url):
-    return settings.SITE_URL + url
+def build_absolute_uri(urlname, args=None, kwargs=None):
+    # Pass prefix='' as a possible SCRIPT_PREFIX (if pretix runs in a subdirectory)
+    # is included in SITE_URL _and_ is added by reverse.
+    return urljoin(settings.SITE_URL, reverse(urlname, args, kwargs, prefix=''))
diff --git a/src/pretix/plugins/paypal/payment.py b/src/pretix/plugins/paypal/payment.py
index 0939f79dc5..22c4b9b9f7 100644
--- a/src/pretix/plugins/paypal/payment.py
+++ b/src/pretix/plugins/paypal/payment.py
@@ -89,8 +89,8 @@ class Paypal(BasePaymentProvider):
                 "payment_method": "paypal",
             },
             "redirect_urls": {
-                "return_url": build_absolute_uri(reverse('plugins:paypal:return')),
-                "cancel_url": build_absolute_uri(reverse('plugins:paypal:abort')),
+                "return_url": build_absolute_uri('plugins:paypal:return'),
+                "cancel_url": build_absolute_uri('plugins:paypal:abort'),
             },
             "transactions": [
                 {
diff --git a/src/pretix/plugins/paypal/views.py b/src/pretix/plugins/paypal/views.py
index ab9695e3c7..273987b837 100644
--- a/src/pretix/plugins/paypal/views.py
+++ b/src/pretix/plugins/paypal/views.py
@@ -71,12 +71,12 @@ def retry(request, order):
                 "payment_method": "paypal",
             },
             "redirect_urls": {
-                "return_url": build_absolute_uri(reverse('plugins:paypal:retry', kwargs={
+                "return_url": build_absolute_uri('plugins:paypal:retry', kwargs={
                     'order': order.code
-                })),
-                "cancel_url": build_absolute_uri(reverse('plugins:paypal:retry', kwargs={
+                }),
+                "cancel_url": build_absolute_uri('plugins:paypal:retry', kwargs={
                     'order': order.code
-                })),
+                }),
             },
             "transactions": [
                 {
diff --git a/src/pretix/plugins/stripe/payment.py b/src/pretix/plugins/stripe/payment.py
index f185fa9c85..73de287deb 100644
--- a/src/pretix/plugins/stripe/payment.py
+++ b/src/pretix/plugins/stripe/payment.py
@@ -40,7 +40,7 @@ class Stripe(BasePaymentProvider):
         return "<div class='alert alert-info'>%s<br /><code>%s</code></div>" % (
             _('Please configure a <a href="https://dashboard.stripe.com/account/webhooks">Stripe Webhook</a> to '
               'the following endpoint in order to automatically cancel orders when a charges are refunded externally.'),
-            build_absolute_uri(reverse('plugins:stripe:webhook'))
+            build_absolute_uri('plugins:stripe:webhook')
         )
 
     def checkout_is_valid_session(self, request):
diff --git a/src/pretix/presale/views/checkout.py b/src/pretix/presale/views/checkout.py
index f297c93a86..8379933745 100644
--- a/src/pretix/presale/views/checkout.py
+++ b/src/pretix/presale/views/checkout.py
@@ -305,7 +305,11 @@ class OrderConfirm(EventViewMixin, CartDisplayMixin, EventLoginRequiredMixin, Ch
                     {
                         'user': request.user, 'order': order,
                         'event': request.event,
-                        'url': build_absolute_uri(self.get_order_url(order)),
+                        'url': build_absolute_uri('presale:event.order', kwargs={
+                            'event': self.request.event.slug,
+                            'organizer': self.request.event.organizer.slug,
+                            'order': order.code,
+                        }),
                         'payment': self.payment_provider.order_pending_mail_render(order)
                     },
                     request.event
diff --git a/src/pretix/presale/views/event.py b/src/pretix/presale/views/event.py
index d295c4179c..2a874de5b8 100644
--- a/src/pretix/presale/views/event.py
+++ b/src/pretix/presale/views/event.py
@@ -188,10 +188,10 @@ class EventForgot(EventViewMixin, TemplateView):
                     {
                         'user': user,
                         'event': self.request.event,
-                        'url': build_absolute_uri(reverse('presale:event.forgot.recover', kwargs={
+                        'url': build_absolute_uri('presale:event.forgot.recover', kwargs={
                             'event': self.request.event.slug,
                             'organizer': self.request.event.organizer.slug,
-                        }) + '?token=' + self.generate_token(user)),
+                        }) + '?token=' + self.generate_token(user),
                     },
                     self.request.event
                 )