Order transaction with multiple currencies

[alexbb77]

I'm using the endpoint ../orders/order_id/transactions.json

with the following payload:

{
    "transaction": {
        "currency": "{{currency}}",
        "gateway": "shopify_payments",
        "kind": "authorization",
        "amount" : "{{amount}}",
        "source" : "external",
        "authorization" : "{{authorization}}"
    }
}

When the order has the "default" currency, the transaction is added fine, but as we are using markets feature and have a second currency set (GBP), when I try to make a transaction to that order I will receive the following error message:

{
    "errors": {
        "currency": [
            "Transactions with source external can't be created for multi currency orders"
        ]
    }
}

So, how is it possible to add a transaction to those orders?

Thank you for the help!