diff --git a/include/zenoh-pico/api/primitives.h b/include/zenoh-pico/api/primitives.h
index 61fb3fa3a..6b8db5f17 100644
--- a/include/zenoh-pico/api/primitives.h
+++ b/include/zenoh-pico/api/primitives.h
@@ -1056,6 +1056,7 @@ int64_t z_bytes_reader_tell(z_bytes_reader_t *reader);
 /**
  * Constructs writer for :c:type:`z_loaned_bytes_t`.
  *
+* Note: reating another writer while previous one is still in use is undefined behaviour.
  * Parameters:
  *   bytes: Data container to write to.
  *   writer: Uninitialized memory location where writer is to be constructed.