Hi, There is a type issue in CollectionProperties which prevents Map objects from being edited. Making sure the types become unboxed fixed the issue for me. Best regards, Christian public Class<?> getType(int index) { if (index < 0 || index > numProperties()) { return null; } if (indexed != null) { Class<?> type = indexed.componentType(); if (type != null) { return type; } } Object obj = getValue(index); if (obj == null) { return Object.class; } // CHANGE: must be unboxed to get accepted by setValue(int, String) return getTypeConversion(obj.getClass()); } public boolean isReadWrite(int index) { if (index < 0 || index > numProperties()) { return false; } if (collection != null) { // collections are not modifiable -- they can't be referenced return false; } // CHANGE: no need to unbox here, already done Class<?> type = getType(index); Object obj = getValue(index); if (obj != null) { // CHANGE: must be unboxed to be assignable to type Class<?> objType = getTypeConversion(obj.getClass()); if (!type.isAssignableFrom(objType)) { return false; } } return !isComposite(index); }