---
title: "google-cloud-texttospeech: model_name Silently Ignored Below v2.28.0"
description: "VoiceSelectionParams.model_name field is silently ignored in google-cloud-texttospeech < 2.28.0; requires ≥ 2.36.0 for reliable behavior"
tags: [google-cloud, tts, python, dependencies, silent-failure]
source: daily/2026-05-08.md
created: 2026-05-08
updated: 2026-05-08
---

# google-cloud-texttospeech: model_name Silently Ignored Below v2.28.0

## The Problem

`VoiceSelectionParams.model_name` (used to select Gemini/Journey voices) is silently ignored in `google-cloud-texttospeech` versions below `2.28.0`. The TTS call succeeds, returns audio — but falls back to a default voice with no error or warning. This makes it look like the voice selection is working when it isn't.

```python
voice = texttospeech.VoiceSelectionParams(
    language_code="en-US",
    model_name="en-US-Journey-F",  # silently ignored if lib < 2.28.0
)
```

## Version Requirements

| Version | Behavior |
|---------|---------|
| < 2.28.0 | `model_name` silently ignored — default voice used |
| 2.28.0–2.35.x | `model_name` accepted but may have edge-case bugs |
| ≥ 2.36.0 | Fully reliable; recommended minimum |

## Fix

In `pyproject.toml`:
```toml
[tool.poetry.dependencies]
google-cloud-texttospeech = ">=2.36.0"
```

After updating:
```bash
poetry lock --no-update   # regenerate lock without upgrading everything else
# Then rebuild the Docker container
docker compose build worker-ai && docker compose up -d worker-ai
```

## Why It Happens

The `model_name` field was added to the proto definition in a later release. Older versions of the generated client simply drop unknown fields when serializing the request — no exception, no warning logged by the client library.

## Diagnostic Signal

If TTS produces audio in a different voice than specified (especially a generic/robotic voice instead of a Journey voice), check the library version first:
```bash
pip show google-cloud-texttospeech | grep Version
```

## Related

- [[wiki/concepts/google-cloud-tts-vs-ai-studio-tts]] — full Cloud TTS vs AI Studio comparison
- [[wiki/concepts/poetry-docker-version-mismatch]] — other silent library version issues
