diff --git a/docs/mkdocs/docs/features/binary_formats/ubjson.md b/docs/mkdocs/docs/features/binary_formats/ubjson.md
index 5f398163f..5fec3cbeb 100644
--- a/docs/mkdocs/docs/features/binary_formats/ubjson.md
+++ b/docs/mkdocs/docs/features/binary_formats/ubjson.md
@@ -141,6 +141,10 @@ The library uses the following mapping from JSON values types to UBJSON types ac
     not passed on: `sax_parse` reports `start_array(0)` (versions before 3.13.0 reported the declared count), and the DOM
     parser reserves nothing for it.
 
+    An optimized array of type `N` (no-op) is empty whatever its count is, because a no-op is not a value. Its count is
+    not passed on: `sax_parse` reports `start_array(0)` (versions before 3.13.0 reported the declared count), and the DOM
+    parser reserves nothing for it.
+
 !!! info "Binary values"
 
     If the JSON data contains the binary type, the value stored is a list of integers, as suggested by the UBJSON