diff --git a/src/main/java/com/alibaba/dashscope/audio/qwen_tts_realtime/QwenTtsRealtimeConfig.java b/src/main/java/com/alibaba/dashscope/audio/qwen_tts_realtime/QwenTtsRealtimeConfig.java
index cf7e187..fcfe9e1 100644
--- a/src/main/java/com/alibaba/dashscope/audio/qwen_tts_realtime/QwenTtsRealtimeConfig.java
+++ b/src/main/java/com/alibaba/dashscope/audio/qwen_tts_realtime/QwenTtsRealtimeConfig.java
@@ -50,8 +50,8 @@ public class QwenTtsRealtimeConfig {
   /** instructions for tts, default is null */
   @Builder.Default String instructions = null;
 
-  /** instructions will optimize on server side, default is null */
-  @Builder.Default String optimizeInstructions = null;
+  /** instructions will optimize on server side, default is false */
+  @Builder.Default boolean optimizeInstructions = false;
 
   /** The extra parameters. */
   @Builder.Default Map<String, Object> parameters = null;
@@ -94,8 +94,8 @@ public JsonObject getConfig() {
       config.put(QwenTtsRealtimeConstants.INSTRUCTIONS, instructions);
     }
 
-    if (optimizeInstructions != null) {
-      config.put(QwenTtsRealtimeConstants.OPTIMIZE_INSTRUCTIONS, optimizeInstructions);
+    if (optimizeInstructions) {
+      config.put(QwenTtsRealtimeConstants.OPTIMIZE_INSTRUCTIONS, true);
     }
 
     if (parameters != null) {