[Ethereum] smart contract address checksum

I am going through ethereum blockchain demo's and currently trying to call other contract deployed already on a local ethereum rpc in memory blockchain.

Using truffle and ethereum rpc i am testing this locally.

I create a contract compile and migrate it locally. then do the following command in powershell which gives me address

MyGameStore.deployed();

address:'0x1d6e1129725897cac1c332b1fcbcf4338d8f96c6'

now i copy above address i use it in my another contract like this

contract IScoreStore{
function GetGameScore(string name) returns(int);
}
 contract MyGameStore{
function showScore(string name) returns(int)
 {    IScoreStore store=    IScoreStore(0x1d6e1129725897cac1c332b1fcbcf4338d8f96c6);
return store.GetGameScore(name);
}
}

however when i do truffle compile , it gives me an error "this looks like an address but has invalid checksum"

My other contract is very much deployed and also it's method's work. then why above error? not sure what i am doing wrong. Can someone help.