Java's MatlabEngine can't access my function

Question

I'm trying to call my matlab void function (which I created) from Java with MatlabEngine like this:

eng.feval("my_funtion",param1,param2,param3);

However, I always get this error:

Undefined function or variable 'my_funtion'.

I thought that the problem was with the parameters, but even when I changed my code to run it without them I got the same error.

Although it works perfectly with Matlab's own function like gcd.