diff --git a/src/document_to_podcast/cli.py b/src/document_to_podcast/cli.py
index 730ce5e..fc4090f 100644
--- a/src/document_to_podcast/cli.py
+++ b/src/document_to_podcast/cli.py
@@ -8,7 +8,13 @@
 from loguru import logger
 
 
-from document_to_podcast.config import Config, Speaker, DEFAULT_PROMPT, DEFAULT_SPEAKERS
+from document_to_podcast.config import (
+    Config,
+    Speaker,
+    DEFAULT_PROMPT,
+    DEFAULT_SPEAKERS,
+    TTS_MODELS,
+)
 from document_to_podcast.inference.model_loaders import (
     load_llama_cpp_model,
     load_parler_tts_model_and_tokenizer,
@@ -24,7 +30,7 @@ def document_to_podcast(
     output_folder: str | None = None,
     text_to_text_model: str = "allenai/OLMoE-1B-7B-0924-Instruct-GGUF/olmoe-1b-7b-0924-instruct-q8_0.gguf",
     text_to_text_prompt: str = DEFAULT_PROMPT,
-    text_to_speech_model: str = "parler-tts/parler-tts-mini-v1",
+    text_to_speech_model: TTS_MODELS = "parler-tts/parler-tts-mini-v1",
     speakers: list[Speaker] | None = None,
     from_config: str | None = None,
 ):
diff --git a/src/document_to_podcast/config.py b/src/document_to_podcast/config.py
index 091b7ea..c57344e 100644
--- a/src/document_to_podcast/config.py
+++ b/src/document_to_podcast/config.py
@@ -42,6 +42,13 @@
 ]
 
 
+TTS_MODELS = Literal[
+    "parler-tts/parler-tts-large-v1",
+    "parler-tts/parler-tts-mini-v1",
+    "parler-tts/parler-tts-mini-v1.1",
+]
+
+
 def validate_input_file(value):
     if Path(value).suffix not in DATA_LOADERS:
         raise ValueError(
@@ -79,10 +86,6 @@ class Config(BaseModel):
     input_file: Annotated[FilePath, AfterValidator(validate_input_file)]
     output_folder: str
     text_to_text_model: Annotated[str, AfterValidator(validate_text_to_text_model)]
-    text_to_text_prompt: str
-    text_to_speech_model: Literal[
-        "parler-tts/parler-tts-large-v1",
-        "parler-tts/parler-tts-mini-v1",
-        "parler-tts/parler-tts-mini-v1.1",
-    ]
+    text_to_text_prompt: Annotated[str, AfterValidator(validate_text_to_text_prompt)]
+    text_to_speech_model: TTS_MODELS
     speakers: list[Speaker]