Proxy Contract Error: error: Internal compiler error: Program erroneously uses uninitialized virtual registers: $r6, $r5

Sway
1

Weird error when trying to compile this proxy contract taken from:

Error:

error: Internal compiler error: Program erroneously uses uninitialized virtual registers: $r6, $r5
Please file an issue on the repository and include the code that triggered this error.

contract;

abi Proxy {
    fn upgrade(contract_id: b256);
}

impl Proxy for Contract {
    fn upgrade(contract_id: b256) {
        asm(r1: 10, r2) {
            add  r2 r1 one;
        }

        /*
         rA: contract id
         rB: index to start copy from, (contract offset)
         rC: amount of bytes to copy (length of code)
         ref: https://fuellabs.github.io/fuel-specs/master/vm/instruction_set.html?highlight=ldc#ldc-load-code-from-an-external-contract
        */
        asm(rA: contract_id, rB, rC) {
            ldc  rA rB rC;
        }
    }
}

Does anyone know what’s going on here?