diff --git a/fluentgen/readme.md b/fluentgen/readme.md
index c88c494650..9ba4acd2c1 100755
--- a/fluentgen/readme.md
+++ b/fluentgen/readme.md
@@ -77,4 +77,5 @@ client-flattened-annotation-target: none
 null-byte-array-maps-to-empty-array: true
 graal-vm-config: true
 stream-style-serialization: true
+use-object-for-unknown: true
 ```