Multisig wallets cannot spend non rct outputs

Question

I'm experimenting with multisig wallet on private testnet. I have followed this tutorial: How to Use Monero Multisignature Wallets (2/2 & 2/3) but when I try to transfer from multisig wallet I get:

{
  error: {
    code: -4,
    message: 'Multisig wallets cannot spend non rct outputs'
  },
  id: 0,
  jsonrpc: '2.0'
}

What's the reason and how can I overcome it?

Answer 1

This was not implemented. Multisig came after rct, so there should not be pre-rct outputs in multisig wallets. It is possible to have code that spends those, it's just that there is no such code currently.