diff --git a/src/pretix/base/models/vouchers.py b/src/pretix/base/models/vouchers.py
index b1b05338c1..fc3b06b356 100644
--- a/src/pretix/base/models/vouchers.py
+++ b/src/pretix/base/models/vouchers.py
@@ -10,10 +10,14 @@ from .items import Item, ItemVariation, Quota
 from .orders import CartPosition, Order, OrderPosition
 
 
-def generate_code():
+def _generate_random_code():
     charset = list('ABCDEFGHKLMNPQRSTUVWXYZ23456789')
+    return get_random_string(length=settings.ENTROPY['voucher_code'], allowed_chars=charset)
+
+
+def generate_code():
     while True:
-        code = get_random_string(length=settings.ENTROPY['voucher_code'], allowed_chars=charset)
+        code = _generate_random_code()
         if not Voucher.objects.filter(code=code).exists():
             return code
 
diff --git a/src/pretix/control/templates/pretixcontrol/vouchers/bulk.html b/src/pretix/control/templates/pretixcontrol/vouchers/bulk.html
index e7d5cc4892..a69f70b6dd 100644
--- a/src/pretix/control/templates/pretixcontrol/vouchers/bulk.html
+++ b/src/pretix/control/templates/pretixcontrol/vouchers/bulk.html
@@ -18,7 +18,7 @@
                                placeholder="{% trans "Number" %}">
                         <div class="input-group-btn">
                             <button class="btn btn-default" type="button" id="voucher-bulk-codes-generate"
-                                data-length="{{ code_length }}">
+                                    data-rng-url="{% url 'control:event.vouchers.rng' organizer=request.event.organizer.slug event=request.event.slug %}">
                                 {% trans "Generate random codes" %}
                             </button>
                         </div>
diff --git a/src/pretix/control/urls.py b/src/pretix/control/urls.py
index c3ba01fb12..0de92b9668 100644
--- a/src/pretix/control/urls.py
+++ b/src/pretix/control/urls.py
@@ -63,6 +63,7 @@ urlpatterns = [
         url(r'^quotas/add$', item.QuotaCreate.as_view(), name='event.items.quotas.add'),
         url(r'^vouchers/$', vouchers.VoucherList.as_view(), name='event.vouchers'),
         url(r'^vouchers/tags/$', vouchers.VoucherTags.as_view(), name='event.vouchers.tags'),
+        url(r'^vouchers/rng$', vouchers.VoucherRNG.as_view(), name='event.vouchers.rng'),
         url(r'^vouchers/(?P<voucher>\d+)/$', vouchers.VoucherUpdate.as_view(), name='event.voucher'),
         url(r'^vouchers/(?P<voucher>\d+)/delete$', vouchers.VoucherDelete.as_view(),
             name='event.voucher.delete'),
diff --git a/src/pretix/control/views/vouchers.py b/src/pretix/control/views/vouchers.py
index 77ba4c5af3..66a3e3789d 100644
--- a/src/pretix/control/views/vouchers.py
+++ b/src/pretix/control/views/vouchers.py
@@ -6,15 +6,18 @@ from django.contrib import messages
 from django.core.urlresolvers import resolve, reverse
 from django.db import transaction
 from django.db.models import Count, Q, Sum
-from django.http import Http404, HttpResponse, HttpResponseRedirect
-from django.utils.formats import date_format
+from django.http import (
+    Http404, HttpResponse, HttpResponseBadRequest, HttpResponseRedirect,
+    JsonResponse,
+)
 from django.utils.timezone import now
 from django.utils.translation import ugettext_lazy as _
 from django.views.generic import (
-    CreateView, DeleteView, ListView, TemplateView, UpdateView,
+    CreateView, DeleteView, ListView, TemplateView, UpdateView, View,
 )
 
 from pretix.base.models import Voucher
+from pretix.base.models.vouchers import _generate_random_code
 from pretix.control.forms.vouchers import VoucherBulkForm, VoucherForm
 from pretix.control.permissions import EventPermissionRequiredMixin
 from pretix.control.signals import voucher_form_class
@@ -261,3 +264,32 @@ class VoucherBulkCreate(EventPermissionRequiredMixin, CreateView):
         # TODO: Transform this into an asynchronous call?
         with request.event.lock():
             return super().post(request, *args, **kwargs)
+
+
+class VoucherRNG(EventPermissionRequiredMixin, View):
+    template_name = 'pretixcontrol/vouchers/bulk.html'
+    permission = 'can_change_vouchers'
+
+    def get(self, request, *args, **kwargs):
+        codes = set()
+        try:
+            num = int(request.GET.get('num', '5'))
+        except ValueError:
+            return HttpResponseBadRequest()
+
+        while len(codes) < num:
+            new_codes = set()
+            for i in range(min(num - len(codes), 500)):  # Work around SQLite's SQLITE_MAX_VARIABLE_NUMBER
+                new_codes.add(_generate_random_code())
+            new_codes -= set([v['code'] for v in Voucher.objects.filter(code__in=new_codes).values('code')])
+            codes |= new_codes
+
+        return JsonResponse({
+            'codes': list(codes)
+        })
+
+    def get_success_url(self) -> str:
+        return reverse('control:event.vouchers', kwargs={
+            'organizer': self.request.event.organizer.slug,
+            'event': self.request.event.slug,
+        })
diff --git a/src/static/pretixcontrol/js/ui/main.js b/src/static/pretixcontrol/js/ui/main.js
index c2475ddab5..01f45f5201 100644
--- a/src/static/pretixcontrol/js/ui/main.js
+++ b/src/static/pretixcontrol/js/ui/main.js
@@ -56,26 +56,11 @@ $(function () {
 
     // Vouchers
     $("#voucher-bulk-codes-generate").click(function () {
-        var charset = "ABCDEFGHKLMNPQRSTUVWXYZ23456789",
-            i = 0, j = 0, len = parseInt($(this).attr("data-length")),
-            num = parseInt($("#voucher-bulk-codes-num").val()), text = "";
-        for (j = 0; j < num; j++) {
-            var key = [];
-            if (window.crypto && window.crypto.getRandomValues && Uint8Array) {
-                key = new Uint8Array(len);
-                window.crypto.getRandomValues(key);
-            } else {
-                for (i = 0; i < len; i++) {
-                    key.push(Math.floor(Math.random() * charset.length));
-                }
-            }
-            if (i > 0) {
-                text += "\n";
-            }
-            for (i = 0; i < len; i++) {
-                text += charset.charAt(key[i] % charset.length);
-            }
-        }
-        $("#id_codes").html(text);
+        var url = $(this).attr("data-rng-url"),
+            num = $("#voucher-bulk-codes-num").val();
+        $("#id_codes").html("Generating...");
+        $.getJSON(url + '?num=' + num, function (data) {
+            $("#id_codes").text(data.codes.join("\n"));
+        });
     });
 });
diff --git a/src/tests/control/test_permissions.py b/src/tests/control/test_permissions.py
index e07d0c2766..c99aae2cba 100644
--- a/src/tests/control/test_permissions.py
+++ b/src/tests/control/test_permissions.py
@@ -55,6 +55,7 @@ event_urls = [
     "vouchers/2/",
     "vouchers/add",
     "vouchers/bulk_add",
+    "vouchers/rng",
     "quotas/",
     "quotas/2/delete",
     "quotas/2/",