[Ethereum] Unable to verify Solidity contract code on etherscan.io

I know this question has been asked many times before. I've read loads of answers, but nothing seems to work for me. I first tried to verify the source code of a much larger, more complex contract, but it didn't work, so I wrote a very simple tiny contract in Solidity:

pragma solidity ^0.4.17;

contract SimpleTest
{
    string public blablabla;
    function SimpleTest() public
    {
        blablabla = "Hello world!";
    }
}

As you can see, I'm not using any constructor arguments, import statements or libraries. I compiled and deployed it using Solidity 0.4.17 from inside Parity. Optimization was enabled. I did not use one of the nightly builds.

Contract creation transaction:

https://etherscan.io/tx/0x2d8615c8bfc548a210781443c872737d890f6c4a5aa373c3d6d20bbaac941b8d

The contract in question:

https://etherscan.io/address/0x5a8b57a6cf17a196e000eca4481257d5d3025636

Link to the verification page:

https://etherscan.io/verifyContract?a=0x5a8b57a6cf17a196e000eca4481257d5d3025636

The error message I get from etherscan.io is:

Sorry! The Compiled Contract ByteCode for 'SimpleTest' does NOT match
the Contract Creation Code for
[0x5a8b57a6cf17a196e000eca4481257d5d3025636]

Contract name(s) found: 'SimpleTest'

Unable to Verify Contract at this point time.

I've analyzed the bytecodes a little bit, and I found that:

• The input data of the contract creation transaction is exactly equal to the bytecode I got from Parity.

• The bytecode that the etherscan.io verifier produces is similar to the bytecode from Parity, and thus also similar to the input data of the contract creation transaction.

• The bytecode on the contract page on etherscan.io is much shorter than the other bytecodes.

• All the bytecodes contain 2 large strings of 00 bytes, except the bytecode on the etherscan.io contract page, it only contains 1 large string of 00 bytes.

I really have no idea what's going on here. Can anyone help?