<bpmn2:extensionElements> fails to load correctly when initialized with moddleExtension

Here is a codesandbox that shows my problem:


When I try to load a diagram which contains the following:

     <pp:element config="%7B%22name%22%3A%22test%22%2C%22trigger%22%3A%22%22%2C%22buttonText%22%3A%22%22%2C%22action%22%3A%22%22%2C%22field%22%3A%22%22%2C%22section%22%3A%22%22%7D" />

then diagram renders with:

<bpmn2:extensionElements />

This can be seen in sandbox by clicking “get xml”.

This only happens when I initialize diagram with Moddle Extensions:

this.modeler = new BpmnModeler({
  container: "#bpmnview",
  keyboard: {
    bindTo: window
  additionalModules: [customControls],
  moddleExtensions: {
    propertyPanel: propertyPanelExtension

If I remove moddleExtensions from initializer, then diagram loads correctly.

Changing the name from element to Element or removing the "tagAlias": "lowerCase" fixes the issue.

  "name": "PropertiesPanel",
  "uri": "http://www.example.com/pp",
  "prefix": "pp",
  "xml": {
    "tagAlias": "lowerCase" // ALTERNATIVELY REMOVE THIS
  "types": [
      "name": "Element", // FIX
      "superClass": ["Element"],
      "properties": [
          "name": "config",
          "isAttr": true,
          "type": "String"
  "emumerations": [],
  "associations": []