diff --git a/AUTHORS b/AUTHORS
index 33763008b..5f09b4042 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -21,3 +21,4 @@ an awesome project. Thank you all!
 	Tobias Kunze <rixx@cutebit.de>
 	Oliver Knapp <github@oliverknapp.de>
 	Vishal Sodani <vishalsodani@rediffmail.com>
+	Jan Felix Wiebe <git@jfwie.be>
diff --git a/src/pretix/control/templates/pretixcontrol/vouchers/bulk.html b/src/pretix/control/templates/pretixcontrol/vouchers/bulk.html
index 6ddf8136f..30b9c43c6 100644
--- a/src/pretix/control/templates/pretixcontrol/vouchers/bulk.html
+++ b/src/pretix/control/templates/pretixcontrol/vouchers/bulk.html
@@ -13,7 +13,7 @@
             <div class="form-group">
                 <div class="col-md-7 col-sm-12 col-md-offset-3">
                     <div class="input-group">
-                        <input type="text" class="form-control input-xs"
+                        <input type="number" class="form-control input-xs"
                                id="voucher-bulk-codes-num"
                                placeholder="{% trans "Number" %}">
                         <div class="input-group-btn">
diff --git a/src/pretix/static/pretixcontrol/js/ui/main.js b/src/pretix/static/pretixcontrol/js/ui/main.js
index 81e366a53..8e5405927 100644
--- a/src/pretix/static/pretixcontrol/js/ui/main.js
+++ b/src/pretix/static/pretixcontrol/js/ui/main.js
@@ -96,12 +96,21 @@ $(function () {
 
     // Vouchers
     $("#voucher-bulk-codes-generate").click(function () {
-        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").val(data.codes.join("\n"));
-        });
+        var num = $("#voucher-bulk-codes-num").val();
+        if (num != "") {
+            $(".form-group:has(#voucher-bulk-codes-num)").addClass("has-error");
+            var url = $(this).attr("data-rng-url");
+            $("#id_codes").html("Generating...");
+            $.getJSON(url + '?num=' + num, function (data) {
+                $("#id_codes").val(data.codes.join("\n"));
+            });
+        } else {
+            $(".form-group:has(#voucher-bulk-codes-num)").addClass("has-error");
+            $("#voucher-bulk-codes-num").focus();
+            setTimeout(function() {
+                $(".form-group:has(#voucher-bulk-codes-num)").removeClass("has-error");
+            }, 3000);
+        }
     });
 
     $("#ajaxerr").on("click", ".ajaxerr-close", ajaxErrDialog.hide);