---
contentType: reference
---

# Item linking errors

n8n displays errors related to data mapping when there are problems tracing an item's linked parent items back through the workflow.

## Errors when pinning data

If you see this error message:
<!-- vale off -->
> ERROR: '`<node-name>`' must be unpinned to execute
<!-- vale on -->
Unpin the data in the named node, and execute the node to get fresh data.

This error has two possible causes:

* The number of inputs into the pinned node has changed since you pinned it.
* You've edited the pinned data and changed the number of items.


## Errors when using the Code node

If you see this error message:

> ERROR: Can't get data for expression under '`<field-name>`' field

You need to supply item linking information yourself, because you have an item linking scenario that n8n can't automatically handle.

To control item linking, set `pairedItem` when returning data. For example, to link to the item at index 0:

```js
[
	{
		"json": {
			. . . 
		},
		// The index of the input item that generated this output item
		"pairedItem": 0
	}
]
```


Refer to [Item linking concepts](/data/data-mapping/data-item-linking/item-linking-concepts/) for a conceptual understanding of item linking, and [Manage item linking in the Code node](/data/data-mapping/data-item-linking/item-linking-code-node/) for detailed guidance on handling item linking.