diff --git a/events/handlers/ap_delivery_handler.py b/events/handlers/ap_delivery_handler.py
index cc8a69a..907f38b 100644
--- a/events/handlers/ap_delivery_handler.py
+++ b/events/handlers/ap_delivery_handler.py
@@ -53,17 +53,20 @@ async def _deliver_to_inbox(
 ) -> bool:
     """POST signed activity to a single inbox. Returns True on success."""
     from shared.utils.http_signatures import sign_request
+    from urllib.parse import urlparse
     import json
 
     body_bytes = json.dumps(body).encode()
     key_id = f"https://{domain}/users/{actor.preferred_username}#main-key"
 
+    parsed = urlparse(inbox_url)
     headers = sign_request(
-        method="POST",
-        url=inbox_url,
-        body=body_bytes,
         private_key_pem=actor.private_key_pem,
         key_id=key_id,
+        method="POST",
+        path=parsed.path,
+        host=parsed.netloc,
+        body=body_bytes,
     )
     headers["Content-Type"] = AP_CONTENT_TYPE