diff --git a/src/servers/app/Desktop.cpp b/src/servers/app/Desktop.cpp
index 33446cca4b..0f2551c27a 100644
--- a/src/servers/app/Desktop.cpp
+++ b/src/servers/app/Desktop.cpp
@@ -2487,6 +2487,8 @@ Desktop::AllWindows()
 Window*
 Desktop::WindowForClientLooperPort(port_id port)
 {
+	AutoReadLocker locker(fWindowLock);
+
 	for (Window* window = fAllWindows.FirstWindow(); window != NULL;
 			window = window->NextWindow(kAllWindowList)) {
 		if (window->ServerWindow()->ClientLooperPort() == port)
diff --git a/src/servers/app/Desktop.h b/src/servers/app/Desktop.h
index b18ae40a8b..fab5c6fc31 100644
--- a/src/servers/app/Desktop.h
+++ b/src/servers/app/Desktop.h
@@ -257,6 +257,7 @@ public:
 			void				WriteWindowOrder(int32 workspace,
 									BPrivate::LinkSender& sender);
 
+			//! The window lock has to be held when accessing a window list!
 			WindowList&			CurrentWindows();
 			WindowList&			AllWindows();