etherchain-light should work in dev mode

[ice09]

When starting parity in dev mode ("immediate mining"), I would like to use etherchain-light, but I get the following error on opening the index page:

invalid block number

Error: invalid block number
    at Object.InvalidResponse (/home/hal9000/etherchain-light/etherchain-light/node_modules/web3/lib/web3/errors.js:35:16)
    at Object.<anonymous> (/home/hal9000/etherchain-light/etherchain-light/node_modules/web3/lib/web3/requestmanager.js:86:36)
    at /home/hal9000/etherchain-light/etherchain-light/node_modules/web3/lib/web3/ipcprovider.js:66:44
    at Array.forEach (native)
    at Socket.<anonymous> (/home/hal9000/etherchain-light/etherchain-light/node_modules/web3/lib/web3/ipcprovider.js:50:47)
    at emitOne (events.js:96:13)
    at Socket.emit (events.js:188:7)
    at readableAddChunk (_stream_readable.js:176:18)
    at Socket.Readable.push (_stream_readable.js:134:10)
    at Pipe.onread (net.js:548:20)