diff --git a/components/terrain/quadtreeworld.hpp b/components/terrain/quadtreeworld.hpp
index 36b2042326..d03ed613d4 100644
--- a/components/terrain/quadtreeworld.hpp
+++ b/components/terrain/quadtreeworld.hpp
@@ -5,6 +5,7 @@
 
 #include <mutex>
 #include <memory>
+#include <atomic>
 
 namespace osg
 {