eth_getTransactionByHash blockNumber is set, even though the transaction isn't mined yet

[pcppcp]

I'm running:

• Parity version: v1.8.0
• Operating system: Linux
• And installed: compiled from source (git branch v1.8.0)
• Chain: Ropsten

According to the JSON RPC specification, blockNumber item returned in the result of eth_getTransactionByHash call should be set to null if the transaction is pending.

In Parity, it is set to an actual block number (probably block id at the time the transaction has been submitted), even though the tx hasn't been mined yet.

>>> transaction_hash = '0xb5430d004d1383aa1955b6827770b578c86711f9eadaca103bcd6bb03e87c859'
# right after the tx has been submitted
>>> tx_pending = self.call('eth_getTransactionByHash', transaction_hash)
# this should be null (or None in python)
>>> tx_pending['blockNumber']                                                                              
u'0x1d67cf'
# wait until the tx is mined
>>> tx_mined = self.call('eth_getTransactionByHash', transaction_hash)
>>> tx_mined['blockNumber']                                                                                       
u'0x1d67d2'

EDIT: this happens only with v1.8.0, v1.7.7 branch behaviour is correct.