Gemini 2.5 Pro TTS Language Codes

Hi

Problem you have encountered:

There seems to be a problem with the Gemini-2.5-pro-tts not recognising language codes.

This is happening in both the production and on the test site versions of the model (link below where this can be reproduced)

https://cloud.google.com/text-to-speech?hl=en

location code set, voice applied and use the default text to generate - it refuses to switch to the correct language code - united kingdom in this case. If you switch models to Gemini-2.5-flash-tts it works.

What you expected to happen:

The voice to speak with a en-gb (united kingdom) voice when generated.

Steps to reproduce:

Using the Gemini-2.5-pro-tts model, use Algenib as the voice, select en-gb as the language code (English (united kingdom)) , let it generate the default text in the demo. Same thing is happening when I try to use the API now.

Other information (workarounds you have tried, documentation consulted, etc):

Tried many work arounds and it does not work - seems to be an issue with the model. This is consistently happening for all voice generations.