diff --git a/ixwebsocket/IXSocketServer.h b/ixwebsocket/IXSocketServer.h
index c8e2ba01..2de83f62 100644
--- a/ixwebsocket/IXSocketServer.h
+++ b/ixwebsocket/IXSocketServer.h
@@ -13,6 +13,7 @@
 #include <mutex>
 #include <functional>
 #include <memory>
+#include <atomic>
 #include <condition_variable>
 
 namespace ix