Issue

When configuring a Reverse ETL sync to the HubSpot Cloud Mode (Actions) destination using the Custom Object V2 action, you may notice that the payload preview displays capitalized display names (such as "First Name" or "Email") in the properties payload instead of HubSpot's strictly required internal property names (such as "firstname" or "email"). This can cause concern that the sync will fail, standard out-of-the-box (OOTB) traits will not update properly, or that duplicate custom properties will be created in HubSpot.

Product

Segment

Environment

Segment Console

Cause

When you map fields in the Segment Console, the properties dropdown dynamically fetches its options directly from HubSpot's API. For human readability, the Segment mapping interface and the preview payload render the capitalized display label. However, when an option is selected from the dropdown, Segment stores the option's true internal value under the hood. The Reverse ETL engine automatically resolves and sends this internal, lowercase name directly into the request body without requiring any manual adjustments.

Resolution

To ensure your HubSpot properties map correctly without creating duplicates, follow these steps:

1. Navigate to the Mappings tab for your Reverse ETL HubSpot destination in the Segment Workspace.
2. Under the Map fields step, ensure you are using the Select Object sub-tab for your properties grid.
3. Select your desired destination fields directly from the provided dropdown list.
4. Save and enable your mapping. You can safely ignore the capitalized display names shown in the payload preview, as Segment will automatically translate these to the correct internal names when the API request is sent.
5. Important: Do not switch to the Customize Object tab to manually type capitalized display labels. If you hand-type a raw key like "First Name" instead of selecting it from the dropdown, that literal string bypasses the automatic value resolution and will be sent directly to HubSpot, which will result in duplicate or mismatched custom properties.

Additional Information 

Because the Custom Object V2 action natively routes batched payloads to HubSpot's bulk endpoints, relying on the pre-populated dropdowns ensures your high-volume syncs process efficiently while maintaining exact schema alignment with HubSpot's internal properties.