speak() doesn't work on Linux

[Jookia]

I downloaded nvgt_0.88.0_beta.tar.gz, extracted it, and ran this script:

#include "speech.nvgt"
void main(){
    speak("Hello from the NVGT speech include!");
}

This doesn't speak anything.

This however works:

void main(){
    screen_reader_speak("Hello from the NVGT speech include!", true);
}

[Jookia]

Looks like this works:

void main(){
    tts_voice voice;
    voice.speak_wait("Hello from the NVGT speech include!", false);
}