diff --git a/src/LLM-API/LLMAPIChatObjectPayload.class.st b/src/LLM-API/LLMAPIChatObjectPayload.class.st
index 4ac3dff..3b03960 100644
--- a/src/LLM-API/LLMAPIChatObjectPayload.class.st
+++ b/src/LLM-API/LLMAPIChatObjectPayload.class.st
@@ -35,6 +35,7 @@ LLMAPIChatObjectPayload >> asJsonableObject [
 	self top_p ifNotNil: [ :v | dic at: #top_p put: v ].
 	self model ifNotNil: [ :v | dic at: #model put: v ].
 	self max_tokens ifNotNil: [ :v | dic at: #max_tokens put: v ].
+	self response_format ifNotNil: [ :v | dic at: #response_format put:  v ].
 	self tools ifNotNil: [ :v | dic at: #tools put: (v collect: #asJsonableObject) ].
 	^ dic
 ]