diff --git a/cortex/push_utils.py b/cortex/push_utils.py
index b533f22..12d6d99 100644
--- a/cortex/push_utils.py
+++ b/cortex/push_utils.py
@@ -67,12 +67,14 @@ def _get_private_key_pem() -> str:
 def _send_one(sub: dict, payload: dict) -> bool:
     """Send a push to a single subscription. Returns False if the endpoint is stale (410)."""
     from pywebpush import webpush, WebPushException
+    from py_vapid import Vapid
 
     try:
+        vapid = Vapid.from_pem(_get_private_key_pem().encode())
         webpush(
             subscription_info=sub,
             data=json.dumps(payload),
-            vapid_private_key=_get_private_key_pem(),
+            vapid_private_key=vapid,
             vapid_claims={"sub": settings.vapid_contact},
         )
         return True