Geth failed to load genesis block

Question

When i try to load genesis block using the following command: geth --datadir privchain init genesis.json, i get the following error,

Fatal: failed to write genesis block: invalid character '.' after object key:value pair

Here is my genesis file:

{
  "config": {
    "chainId": 15,
    "homesteadBlock": 0,
    "eip155Block": 0,
    "eip158Block": 0
  },
  "difficulty": "200000000",
  "gasLimit": "2100000",
  "alloc": {
    "af8bd873406715dc1444077bb9d65c8800f7acdf": {
      "balance": "400000"
    }
  }
}

I am using this genesis file from this link: https://github.com/ethereum/go-ethereum/wiki/Private-network can someone help me out here please? Thank you