Datatype problem with arduino and coder.ceval

Hello, I'm writing a simulink device driver block for Arduino Due with the Matlab Function Approach as explained in the Simulink Device Driver guide. When I want to pass a double from the C++ code to the matlab function code with coder.ceval() I get a wrong number. Here is an example:

C++ function:

    #include <Arduino.h>

    extern "C" double dout_output()
    {
    return 50.5;
    }

Matlab function in Simulink:

    function x = example()

    x = 0.0;
    if strcmp(coder.target,'rtw'),

    x = coder.ceval('dout_output');
    end

When I run this code in external mode on an adruino due I don't get the 50.5 but a large number like 1113794816. Any sugestions?