diff --git a/client/CustomGoogleGeminiClient.js b/client/CustomGoogleGeminiClient.js
index 871abfe..8853063 100644
--- a/client/CustomGoogleGeminiClient.js
+++ b/client/CustomGoogleGeminiClient.js
@@ -169,11 +169,6 @@ export class CustomGoogleGeminiClient extends GoogleGeminiClient {
        * @type Array<Content>
        */
       contents: history,
-      system_instruction: {
-        parts: {
-          text: systemMessage
-        }
-      },
       safetySettings: [
         {
           category: HarmCategory.HARM_CATEGORY_DANGEROUS_CONTENT,
@@ -204,6 +199,13 @@ export class CustomGoogleGeminiClient extends GoogleGeminiClient {
       },
       tools: []
     }
+    if (systemMessage) {
+      body.system_instruction = {
+        parts: {
+          text: systemMessage
+        }
+      }
+    }
     if (this.tools?.length > 0) {
       body.tools.push({
         function_declarations: this.tools.map(tool => tool.function())