diff --git a/src/window.cpp b/src/window.cpp
--- a/src/window.cpp
+++ b/src/window.cpp
@@ -1347,7 +1347,7 @@ void ResizeWindow(Window *w, int x, int 
 	w->SetDirty();
 }
 
-static bool _dragging_window;
+static bool _dragging_window; ///< A window is being dragged or resized.
 
 static bool HandleWindowDragging()
 {