diff --git a/fluid/Fl_Window_Type.cxx b/fluid/Fl_Window_Type.cxx
index 36a7338c9..bfcea17bc 100644
--- a/fluid/Fl_Window_Type.cxx
+++ b/fluid/Fl_Window_Type.cxx
@@ -503,7 +503,11 @@ void Overlay_Window::resize(int X,int Y,int W,int H) {
   Fl_Widget* t = resizable(); resizable(0);
   Fl_Overlay_Window::resize(X,Y,W,H);
   resizable(t);
-  set_modflag(1);
+  // do not set the mod flag if the window was not resized. In FLUID, all
+  // windows are opened without a given x/y position, so modifying x/y
+  // should not mark the project as dirty
+  if (W!=w() || H!=h())
+    set_modflag(1);
   update_xywh();
 }