Concatenate string and var less css

Can anyone please tell me how to concatenate a var and a string in LESS so I don't have the space between them?

I have the following code:

.text(@size) {
    font-size: @size + px;
    line-height: (@size / 10) + em;
}

h1 {
   .text(16)
}

What the LESS outputs is the following:

h1 {
    font-size: 12 px;
    line-height: 1.2 em;
}

I need to find a way to remove the spaces.

Thanks Pete