diff --git a/python/cog/server/clients.py b/python/cog/server/clients.py
index e28e3994e..8c01e6c64 100644
--- a/python/cog/server/clients.py
+++ b/python/cog/server/clients.py
@@ -148,7 +148,8 @@ async def upload_file(self, fh: io.IOBase, url: Optional[str]) -> str:
         fh.seek(0)
         # try to guess the filename of the given object
         name = getattr(fh, "name", "file")
-        filename = os.path.basename(name)
+        filename = os.path.basename(name) or "file"
+        assert isinstance(filename, str)
 
         guess, _ = mimetypes.guess_type(filename)
         content_type = guess or "application/octet-stream"
@@ -179,7 +180,7 @@ async def chunk_file_reader() -> AsyncIterator[bytes]:
                 headers={"Content-Type": content_type},
                 follow_redirects=False,
             )
-            if resp1.status_code == 307:
+            if resp1.status_code == 307 and resp1.headers["Location"]:
                 url = resp1.headers["Location"]
         resp = await self.file_client.put(
             url,
diff --git a/python/cog/server/runner.py b/python/cog/server/runner.py
index 52b91a7a8..e1401a582 100644
--- a/python/cog/server/runner.py
+++ b/python/cog/server/runner.py
@@ -335,8 +335,9 @@ def cancel(self, prediction_id: str) -> None:
         if id not in self._predictions_in_flight:
             log.warn("can't cancel %s (%s)", prediction_id, self._predictions_in_flight)
             raise UnknownPredictionError()
-        if self._child.is_alive() and self._child.pid is not None:
-            os.kill(self._child.pid, signal.SIGUSR1)
+        maybe_pid = self._child.pid
+        if self._child.is_alive() and maybe_pid is not None:
+            os.kill(maybe_pid, signal.SIGUSR1)
             log.info("sent cancel")
             self._events.send(Cancel(prediction_id))
             # maybe this should probably check self._semaphore._value == self._concurrent
@@ -396,7 +397,8 @@ def __init__(
 
         self._client_manager = client_manager
         self._webhook_sender = client_manager.make_webhook_sender(
-            request.webhook, request.webhook_events_filter
+            request.webhook,
+            request.webhook_events_filter or schema.WebhookEvent.default_events(),
         )
         self._upload_url = upload_url
         self._output_type = None