diff --git a/Elwig/Windows/PaymentVariantsWindow.xaml.cs b/Elwig/Windows/PaymentVariantsWindow.xaml.cs
index 3c8e7c3..349a526 100644
--- a/Elwig/Windows/PaymentVariantsWindow.xaml.cs
+++ b/Elwig/Windows/PaymentVariantsWindow.xaml.cs
@@ -291,9 +291,12 @@ namespace Elwig.Windows {
             }
             try {
                 var json = BillingData.ParseJson(DataInput.Text);
-                var origJson = BillingData.ParseJson(v.Data);
+                var origJson = v.Data;
+                try {
+                    origJson = JsonSerializer.Serialize(BillingData.ParseJson(v.Data));
+                } catch { }
                 DataValid = true;
-                if (JsonSerializer.Serialize(json) != JsonSerializer.Serialize(origJson)) {
+                if (JsonSerializer.Serialize(json) != origJson) {
                     ControlUtils.SetInputChanged(DataInput);
                     DataChanged = true;
                 } else {