Why is my C code from dpigen not giving different random values when I run it multiple times?

I am using Matlab R2019a to generate DPI C functions. I am generating C code from this function:

function stimulus = get_stimulus()
    stimulus = rand(1,100);
end

However the C function doesn't behave as I expected. The value stimulus gives an array of 100 random-looking values, but when I run the test calling it multiple times, I get the same array each time.

I see a function named 'b_rand', and somewhere else in the comments I see:

This is a uniform (0,1) pseudorandom number generator

So it looks like this should be truly random, and I should get different outputs each time I run the test.

If it helps, I make calls to the C code like this. This is in a SystemVerilog testbench.

import stimulus_dpi_pkg::*;

chandle stim_objhandle=null;
real stimulus [0:99];

stim_objhandle=DPI_stimulus_initialize(stim_objhandle);

// Call the DPI function to get the simulus
DPI_stimulus(stim_objhandle,stimulus);

// Clean up DPIC function
DPI_stimulus_terminate(stim_objhandle);

Is this the expected behavior? If not, how do I fix it?