diff --git a/common/src/main/java/dev/langchain4j/provider/OpenAiModelFactory.java b/common/src/main/java/dev/langchain4j/provider/OpenAiModelFactory.java
index c55f5a3c8..ef8a8414b 100644
--- a/common/src/main/java/dev/langchain4j/provider/OpenAiModelFactory.java
+++ b/common/src/main/java/dev/langchain4j/provider/OpenAiModelFactory.java
@@ -30,7 +30,7 @@ public class OpenAiModelFactory implements ModelFactory, InitializingBean {
                 .timeout(Duration.ofSeconds(modelConfig.getTimeOut()))
                 .logRequests(modelConfig.getLogRequests())
                 .logResponses(modelConfig.getLogResponses());
-        if (modelConfig.getJsonFormat()) {
+        if (modelConfig.getJsonFormat() != null && modelConfig.getJsonFormat()) {
             openAiChatModelBuilder.strictJsonSchema(true)
                     .responseFormat(modelConfig.getJsonFormatType());
         }