Custom Field Dropdown list all selections as undefined

[Jackie Gage]

when setting up a new employee in Trello. i build automations around there name. i added there name to the Dropdown selection list in my Custom Field and i can see and select all the names when i do it from a card itself but when i try to select anyone's name from the list via the Automation builder all the dropdown options show "Undefined"  there have been no other changes to Trello on our end. i did try to clear cache and use Incognito mode. still get the same "Undefined" results.  

[Anwesha Pan · Accepted solution]

Hi @Jackie Gage 👋🏻

This is a known Trello bug where the Automation builder doesn't properly render custom field dropdown option labels — they show as "Undefined" even though the options work perfectly fine when selecting directly on a card. It's not caused by anything on your end, and clearing cache/incognito won't fix it since it's a server-side rendering issue in the Automation builder UI.

Here are some workarounds to keep your onboarding automations moving:

1. The "Undefined" options still map correctly — even though they display as "Undefined" in the Automation builder, the underlying values are typically still there. If you know the order you added names to the dropdown, you can try selecting the correct positional "Undefined" entry and test-run the automation to confirm it sets the right value.

2. Use the Trello API instead — since you're comfortable with tooling, you can reference the custom field option by its ID in the automation's API-level configuration. You can get the option IDs by calling GET /1/boards/{boardId}/customFields and then looking at the options array for your dropdown field. Each option has an id and a value.text — use the id to target the correct name.

3. Try recreating the custom field — some users have resolved this by deleting and re-adding the dropdown custom field with the same options. This can force Trello to re-index the option labels for the Automation builder. Be aware this will clear existing values on cards, so export/note the current data first.

4. Report it to Atlassian Support — since this is a platform bug, filing a support ticket at Atlassian Support will help get it tracked. Include a screenshot of the "Undefined" dropdown in the Automation builder vs. the working dropdown on a card — that contrast makes the report very clear.

I hope this helps & resolves your issue. 🙂

Thanks,
Anwesha