diff --git a/thermal/aidl/default/Thermal.h b/thermal/aidl/default/Thermal.h
index 788af4a..8885e63 100644
--- a/thermal/aidl/default/Thermal.h
+++ b/thermal/aidl/default/Thermal.h
@@ -54,7 +54,8 @@
             const std::shared_ptr<IThermalChangedCallback>& in_callback) override;
 
   private:
-    std::set<std::shared_ptr<IThermalChangedCallback>> mCallbacks;
+    std::mutex thermal_callback_mutex_;
+    std::vector<std::shared_ptr<IThermalChangedCallback>> thermal_callbacks_;
 };
 
 }  // namespace example