diff --git a/src/fastapi_poe/base.py b/src/fastapi_poe/base.py
index 01a8a53..ced6269 100644
--- a/src/fastapi_poe/base.py
+++ b/src/fastapi_poe/base.py
@@ -31,6 +31,10 @@
 logger = logging.getLogger("uvicorn.default")
 
 
+class InvalidParameterError(Exception):
+    pass
+
+
 class LoggingMiddleware(BaseHTTPMiddleware):
     async def set_body(self, request: Request):
         receive_ = await request._receive()
@@ -126,32 +130,28 @@ async def post_message_attachment(
     async def _make_file_attachment_request(
         self, access_key, message_id, download_url=None, file_data=None, filename=None
     ):
-        assert download_url or (
-            file_data and filename
-        ), "Must provide either download_url or file_data and filename."
-
-        if file_data:
-            assert filename, "Must provide filename if providing file_data."
-
-        if download_url:
-            assert (
-                not file_data and not filename
-            ), "Cannot provide file_data or filename if providing download_url."
-
         url = "https://www.quora.com/poe_api/file_attachment_POST"
 
         async with httpx.AsyncClient(timeout=120) as client:
             try:
                 headers = {"Authorization": f"{access_key}"}
                 if download_url:
+                    if file_data or filename:
+                        raise InvalidParameterError(
+                            "Cannot provide filename or file_data if download_url is provided."
+                        )
                     data = {"message_id": message_id, "download_url": download_url}
                     request = httpx.Request("POST", url, data=data, headers=headers)
-                else:
+                elif file_data and filename:
                     data = {"message_id": message_id}
                     files = {"file": (filename, file_data)}
                     request = httpx.Request(
                         "POST", url, files=files, data=data, headers=headers
                     )
+                else:
+                    raise InvalidParameterError(
+                        "Must provide either download_url or file_data and filename."
+                    )
                 response = await client.send(request)
 
                 if response.status_code != 200:
@@ -162,15 +162,18 @@ async def _make_file_attachment_request(
                 return response
             except httpx.HTTPError:
                 logger.error("An HTTP error occurred when attempting to attach file")
+                raise
 
     async def _process_pending_attachment_requests(self, message_id):
         try:
             await asyncio.gather(*self.pending_file_attachments.get(message_id, []))
         except Exception:
             logger.error("Error processing pending attachment requests")
-        # clear the pending attachments for the message
-        async with self.file_attachment_lock:
-            self.pending_file_attachments.pop(message_id, None)
+            raise
+        finally:
+            # clear the pending attachments for the message
+            async with self.file_attachment_lock:
+                self.pending_file_attachments.pop(message_id, None)
 
     @staticmethod
     def text_event(text: str) -> ServerSentEvent:
@@ -271,7 +274,11 @@ async def handle_query(
         except Exception as e:
             logger.exception("Error responding to query")
             yield self.error_event(repr(e), allow_retry=False)
-        await self._process_pending_attachment_requests(request.message_id)
+        try:
+            await self._process_pending_attachment_requests(request.message_id)
+        except Exception as e:
+            logger.exception("Error processing pending attachment requests")
+            yield self.error_event(repr(e), allow_retry=False)
         yield self.done_event()