Unable to get the model function parameter value

[eluser]shadowchest[/eluser]
In a model file, I have a function functionname($param=false) { echo $param; }. In a controller file, I call the function by return $this->modelname->functionname(true); This should return a "true" value since I set the parameter to true, but still it returns false. Any idea?

I am using CI Version 1.7.3, by the way.