leekelleher
September 28, 2026, 2:34pm
9
Quick follow up on this.
When Umbraco’s TypeFinder detects a custom class/DTO that implements an IDictionary<string, object>, it will trigger a polymorphism check, which is what threw the original error.(I see this as an edge-case, not something the majority of users will experience).
Following the issue through with @jrunestone , we reached a fix and it’s resolved in Contentment v6.3.3 (and v7.2.1) .
More details on the repo:
opened 05:56PM - 22 Sep 26 UTC
closed 08:48PM - 24 Sep 26 UTC
type/bug-report
### Which Contentment version are you using?
6.3.0
### Which Umbraco version a… re you using? Be specific: e.g. 16.3.4, (not v16)
17.6.2
### Bug summary
Hi there,
After upgrading and entering backoffice the request to /umbraco/management/api/v1/manifest/manifest/private fails with a 500 error. The response JSON is broken right in the middle of the contentment section. If I remove the Contentment nugets the error goes away. The logs give me a `NotSupportedException` with the message `Runtime type 'System.Collections.Generic.Dictionary`2[System.String,System.Object]' is not supported by polymorphic type 'System.Collections.Generic.IDictionary`2[System.String,System.Object]'. Path: $.meta.Fields.Config.`
I have a couple of custom datatypes configured that I migrated to use `IContentmentDataSource`, but even when removing them (both from the backoffice and database and also commenting out the data source code) the error remains. This only happens when Umbraco isn’t in development mode, i.e on localhost it works fine.
I looked but couldn’t find any specific migration steps, am I missing something?
I'm not using uSync.
Snippet from the manifest request:
```json
{
"name": "Contentment",
"id": "Umbraco.Community.Contentment",
"version": "6.3.0",
"cacheBuster": "6.3.0",
"extensions": [
{
"type": "bundle",
"alias": "Umb.Contentment.Bundle",
"name": "[Contentment] Bundle",
"js": "/App_Plugins/Contentment/manifests.js"
},
{
"type": "menuItem",
"alias": "Umb.Contentment.MenuItem.Contentment",
"name": "[Contentment] Menu Item",
"meta": {
"label": "Contentment",
"icon": "icon-contentment",
"entityType": "contentment",
"menus": [
"Umb.Menu.AdvancedSettings"
]
}
}{
"type": "Error",
"title": "Server Error",
"status": 500
}
```
### Steps to reproduce
This happens after a migration from Umbraco 13 to Umbraco 17 and Contentment 6.*.
### Expected result / actual result
_No response_