diff --git a/prod/clean_arch/dita_v2/rust_backend.py b/prod/clean_arch/dita_v2/rust_backend.py
index 4985e98..401febf 100644
--- a/prod/clean_arch/dita_v2/rust_backend.py
+++ b/prod/clean_arch/dita_v2/rust_backend.py
@@ -219,7 +219,8 @@ class _RustKernelLib:
         return json.loads(self._take_string(raw))
 
     def set_slot_json(self, handle: ctypes.c_void_p, slot_id: int, payload: Dict[str, Any]) -> None:
-        rc = self.lib.dita_kernel_set_slot_json(handle, ctypes.c_size_t(slot_id), ctypes.c_char_p(_to_rust_bytes(payload)))
+        _pb = _to_rust_bytes(payload)
+        rc = self.lib.dita_kernel_set_slot_json(handle, ctypes.c_size_t(slot_id), ctypes.c_char_p(_pb))
         if rc != 0:
             raise RuntimeError(f"dita_kernel_set_slot_json failed rc={rc}")