diff --git a/letta/client/client.py b/letta/client/client.py
index 0bf773c0..7fecbc23 100644
--- a/letta/client/client.py
+++ b/letta/client/client.py
@@ -434,6 +434,7 @@ class RESTClient(AbstractClient):
         debug: bool = False,
         default_llm_config: Optional[LLMConfig] = None,
         default_embedding_config: Optional[EmbeddingConfig] = None,
+        headers: Optional[Dict] = None,
     ):
         """
         Initializes a new instance of Client class.
@@ -442,12 +443,16 @@ class RESTClient(AbstractClient):
             auto_save (bool): Whether to automatically save changes.
             user_id (str): The user ID.
             debug (bool): Whether to print debug information.
-            default
+            default_llm_config (Optional[LLMConfig]): The default LLM configuration.
+            default_embedding_config (Optional[EmbeddingConfig]): The default embedding configuration.
+            headers (Optional[Dict]): The additional headers for the REST API.
         """
         super().__init__(debug=debug)
         self.base_url = base_url
         self.api_prefix = api_prefix
         self.headers = {"accept": "application/json", "authorization": f"Bearer {token}"}
+        if headers:
+            self.headers.update(headers)
         self._default_llm_config = default_llm_config
         self._default_embedding_config = default_embedding_config
 
diff --git a/letta/server/rest_api/routers/v1/sources.py b/letta/server/rest_api/routers/v1/sources.py
index 48f05c56..68a94a9e 100644
--- a/letta/server/rest_api/routers/v1/sources.py
+++ b/letta/server/rest_api/routers/v1/sources.py
@@ -37,7 +37,10 @@ def get_source(
     """
     actor = server.get_user_or_default(user_id=user_id)
 
-    return server.source_manager.get_source_by_id(source_id=source_id, actor=actor)
+    source = server.source_manager.get_source_by_id(source_id=source_id, actor=actor)
+    if not source:
+        raise HTTPException(status_code=404, detail=f"Source with id={source_id} not found.")
+    return source
 
 
 @router.get("/name/{source_name}", response_model=str, operation_id="get_source_id_by_name")
@@ -52,6 +55,8 @@ def get_source_id_by_name(
     actor = server.get_user_or_default(user_id=user_id)
 
     source = server.source_manager.get_source_by_name(source_name=source_name, actor=actor)
+    if not source:
+        raise HTTPException(status_code=404, detail=f"Source with name={source_name} not found.")
     return source.id
 
 
@@ -94,6 +99,8 @@ def update_source(
     Update the name or documentation of an existing data source.
     """
     actor = server.get_user_or_default(user_id=user_id)
+    if not server.source_manager.get_source_by_id(source_id=source_id, actor=actor):
+        raise HTTPException(status_code=404, detail=f"Source with id={source_id} does not exist.")
     return server.source_manager.update_source(source_id=source_id, source_update=source, actor=actor)