diff --git a/litellm/llms/text_to_speech/vertex_ai.py b/litellm/llms/text_to_speech/vertex_ai.py
index 01ab6edc05..139f3bbc2b 100644
--- a/litellm/llms/text_to_speech/vertex_ai.py
+++ b/litellm/llms/text_to_speech/vertex_ai.py
@@ -54,7 +54,7 @@ class VertexTextToSpeechAPI(VertexLLM):
         timeout: Union[float, httpx.Timeout],
         model: str,
         input: str,
-        voice: str,
+        voice: Optional[str] = None,
         _is_async: Optional[bool] = False,
         optional_params: Optional[dict] = None,
         **kwargs,
diff --git a/litellm/main.py b/litellm/main.py
index 4323c24a6b..f9ad007d6c 100644
--- a/litellm/main.py
+++ b/litellm/main.py
@@ -4699,7 +4699,7 @@ async def aspeech(*args, **kwargs) -> HttpxBinaryResponseContent:
 def speech(
     model: str,
     input: str,
-    voice: str,
+    voice: Optional[str] = None,
     api_key: Optional[str] = None,
     api_base: Optional[str] = None,
     api_version: Optional[str] = None,
@@ -4735,6 +4735,12 @@ def speech(
     logging_obj = kwargs.get("litellm_logging_obj", None)
     response: Optional[HttpxBinaryResponseContent] = None
     if custom_llm_provider == "openai":
+        if voice is None:
+            raise litellm.BadRequestError(
+                message="'voice' is required for OpenAI TTS",
+                model=model,
+                llm_provider=custom_llm_provider,
+            )
         api_base = (
             api_base  # for deepinfra/perplexity/anyscale/groq/friendliai we check in get_llm_provider and pass in the api base from there
             or litellm.api_base
@@ -4781,6 +4787,12 @@ def speech(
         )
     elif custom_llm_provider == "azure":
         # azure configs
+        if voice is None:
+            raise litellm.BadRequestError(
+                message="'voice' is required for Azure TTS",
+                model=model,
+                llm_provider=custom_llm_provider,
+            )
         api_base = api_base or litellm.api_base or get_secret("AZURE_API_BASE")  # type: ignore
 
         api_version = (