diff --git a/plugins/rendermax/renderer_light.hpp b/plugins/rendermax/renderer_light.hpp
index f6a158d7f5..5d6799ec93 100644
--- a/plugins/rendermax/renderer_light.hpp
+++ b/plugins/rendermax/renderer_light.hpp
@@ -266,7 +266,7 @@ class lightThread
     void combine(); //combine existing canvas into global lightmap
 public:
     std::thread *myThread;
-    bool isDone; //no mutex, because bool is atomic
+    std::atomic<bool> isDone;
     lightThread(lightThreadDispatch& dispatch);
     ~lightThread();
     void run();