Failure to recover signature address, for web3.accounts.{sign/recover}

[coventry]

Hi, I'd be grateful for an explanation of how to recover the signature address from a signature object. Intuitively, I would have expected this to work:

truffle(test)> // This is with the second account from traditional truffle seed mnemonic, "candy maple cake sugar pudding cream honey rich smooth crumble sweet treat"
truffle(test)> signatureObject = web3.eth.accounts.sign("Hello world", "0xf17f52151EbEF6C7334FAD080c5704D77216b732")
{ message: 'Hello world',
  messageHash: '0x8144a6fa26be252b86456491fbcd43c1de7e022241845ffea1c3df066f7cfede',
  v: '0x1c',
  r: '0x1239d9e6d7a8e881a60759479678397139d11964dd95636d92975d66561a8e76',
  s: '0x7013924aa3423231e8afbd0be50ebe46ddca025252d241c611533e38e6a6f464',
  signature: '0x1239d9e6d7a8e881a60759479678397139d11964dd95636d92975d66561a8e767013924aa3423231e8afbd0be50ebe46ddca025252d241c611533e38e6a6f4641c' }
truffle(test)> ////////////////////////////////////////////////////////////////////////
truffle(test)> // !!! Does not recover "0xf17f52151EbEF6C7334FAD080c5704D77216b732" !!!
truffle(test)> web3.eth.accounts.recover(signatureObject)
'0x9f5F258D9e092c64E577533F0035184b8a7963aD'
truffle(test)> ////////////////////////////////////////////////////////////////////////
truffle(test)> web3.version
'1.0.0-beta.37'

This is with versions Truffle v5.0.0-next.19 (core: 5.0.0-beta.2) and Node v8.10.0, in case it's relevant.

[coventry]

I see my error in the example: using the public instead of the private key. I had tested that, but without the 0x key. Would you take a PR to fail if there's no 0x prefix, or refrain from truncating the first two characters (assuming that's the issue?)