diff --git a/XSDVisualiser.Desktop/Views/LeftTreeView.axaml.cs b/XSDVisualiser.Desktop/Views/LeftTreeView.axaml.cs
index 4485cf5..b24ee8b 100644
--- a/XSDVisualiser.Desktop/Views/LeftTreeView.axaml.cs
+++ b/XSDVisualiser.Desktop/Views/LeftTreeView.axaml.cs
@@ -370,9 +370,15 @@ public partial class LeftTreeView : UserControl
         await writer.FlushAsync();
     }
 
+    private static string SanitizeXmlLocalName(string? name, string fallback)
+    {
+        var candidate = string.IsNullOrWhiteSpace(name) ? fallback : name!;
+        return XmlConvert.EncodeLocalName(candidate);
+    }
+
     private static void WriteElementRecursive(XmlWriter writer, SchemaNode node)
     {
-        var localName = string.IsNullOrWhiteSpace(node.Name) ? "Element" : node.Name!;
+        var localName = SanitizeXmlLocalName(node.Name, "Element");
         if (!string.IsNullOrEmpty(node.Namespace))
             writer.WriteStartElement(localName, node.Namespace);
         else
@@ -381,7 +387,7 @@ public partial class LeftTreeView : UserControl
         // Write attributes if any (use type + constraints as placeholder value)
         foreach (var attr in node.Attributes)
         {
-            var attrName = string.IsNullOrWhiteSpace(attr.Name) ? "attr" : attr.Name!;
+            var attrName = SanitizeXmlLocalName(attr.Name, "attr");
             var value = BuildTypeAndConstraintText(attr.BuiltInType ?? attr.TypeName, attr.Constraints);
             if (!string.IsNullOrEmpty(attr.Namespace))
                 writer.WriteAttributeString(attrName, attr.Namespace, value);