Unable to register same function name with different parameters

[alexdupre]

When I try to add the following signatures on https://www.4byte.directory/submit/ :

function addLiquidityNAT(
        address token,
        uint256 amountTokenDesired,
        uint256 amountTokenMin,
        uint256 amountNATMin,
        address to,
        uint256 deadline
    )
        external
        payable
        returns (
            uint256 amountToken,
            uint256 amountNAT,
            uint256 liquidity
        )

I get the following message:

Function signature addLiquidityNAT(address,uint256,uint256,uint256,address,uint256,uint256,uint256) already exists.

But actually this is a different function, the parameters and the function signature are different.