diff --git a/src/blackgui/models/listmodelbase.cpp b/src/blackgui/models/listmodelbase.cpp
index a26797df2..2dfd061d0 100644
--- a/src/blackgui/models/listmodelbase.cpp
+++ b/src/blackgui/models/listmodelbase.cpp
@@ -752,13 +752,15 @@ namespace BlackGui
         template <typename ObjectType, typename ContainerType, bool UseCompare>
         QJsonObject CListModelBase<ObjectType, ContainerType, UseCompare>::toJson() const
         {
-            return container().toJson();
+            const CVariant variant = CVariant::fromValue(container());
+            return variant.toJson();
         }
 
         template <typename ObjectType, typename ContainerType, bool UseCompare>
         QString CListModelBase<ObjectType, ContainerType, UseCompare>::toJsonString(QJsonDocument::JsonFormat format) const
         {
-            return container().toJsonString(format);
+            const CVariant variant = CVariant::fromValue(container());
+            return variant.toJsonString(format);
         }
 
         template <typename ObjectType, typename ContainerType, bool UseCompare>
diff --git a/src/blackgui/views/viewbase.cpp b/src/blackgui/views/viewbase.cpp
index 82cb50520..6ba375b13 100644
--- a/src/blackgui/views/viewbase.cpp
+++ b/src/blackgui/views/viewbase.cpp
@@ -1405,10 +1405,22 @@ namespace BlackGui
                     m = CStatusMessage(this).warning("Reading '%1' yields no data") << fileName;
                     break;
                 }
+                if (!Json::looksLikeSwiftJson(json))
+                {
+                    m = CStatusMessage(this).warning("No swift JSON '%1'") << fileName;
+                    break;
+                }
                 try
                 {
-                    ContainerType container;
-                    container.convertFromJson(json);
+                    CVariant containerVariant;
+                    containerVariant.convertFromJson(Json::jsonObjectFromString(json));
+                    if (!containerVariant.canConvert<ContainerType>())
+                    {
+                        m = CStatusMessage(this).warning("No valid swift JSON '%1'") << fileName;
+                        break;
+                    }
+
+                    ContainerType container = containerVariant.value<ContainerType>();
                     m = this->modifyLoadedJsonData(container);
                     if (m.isFailure()) { break; } // modification error
                     m = this->validateLoadedJsonData(container);
@@ -1436,8 +1448,8 @@ namespace BlackGui
                                      tr("Save data file"), getDefaultFilename(false),
                                      tr("swift (*.json *.txt)"));
             if (fileName.isEmpty()) { return CStatusMessage(this, CStatusMessage::SeverityDebug, "Save canceled", true); }
-            const QString json(this->toJsonString());
-            bool ok = CFileUtils::writeStringToFileInBackground(json, fileName);
+            const QString json(this->toJsonString()); // save as CVariant JSON
+            const bool ok = CFileUtils::writeStringToFileInBackground(json, fileName);
             if (ok)
             {
                 return CStatusMessage(this, CStatusMessage::SeverityInfo, "Writing " + fileName + " in progress", true);