Functional test error when modifying RPC response: "RPC key returned that was not in doc"

I modified an RPC call response for a PR, but some functional tests are failing. The error I'm getting is:

  File "/home/sliv3r/Documentos/Projectes/BitcoinCore/bitcoin/build/test/functional/feature_fee_estimation.py", line 203, in initial_split
    self.confutxo = self.wallet.send_self_transfer_multi(
  File "/home/sliv3r/Documentos/Projectes/BitcoinCore/bitcoin/test/functional/test_framework/wallet.py", line 295, in send_self_transfer_multi
    self.sendrawtransaction(from_node=from_node, tx_hex=tx["hex"])
  File "/home/sliv3r/Documentos/Projectes/BitcoinCore/bitcoin/test/functional/test_framework/wallet.py", line 397, in sendrawtransaction
    self.scan_tx(from_node.decoderawtransaction(tx_hex))
  File "/home/sliv3r/Documentos/Projectes/BitcoinCore/bitcoin/test/functional/test_framework/coverage.py", line 50, in __call__
    return_val = self.auth_service_proxy_instance.__call__(*args, **kwargs)
  File "/home/sliv3r/Documentos/Projectes/BitcoinCore/bitcoin/test/functional/test_framework/authproxy.py", line 146, in __call__
    raise JSONRPCException(response['error'], status)
test_framework.authproxy.JSONRPCException: Internal bug detected: RPC call "decoderawtransaction" returned incorrect type:
{
    "vin": {
        "0": {
            "witScript": "key returned that was not in doc"
        },
        "1": {
            "witScript": "key returned that was not in doc"
        }
    }
}

I am unable to find where the expected answers for RPC are defined. Where can I find this "doc"?