diff --git a/lcl/interfaces/gtk/gtkglobals.pp b/lcl/interfaces/gtk/gtkglobals.pp
index 943a79e20f..7917f48180 100644
--- a/lcl/interfaces/gtk/gtkglobals.pp
+++ b/lcl/interfaces/gtk/gtkglobals.pp
@@ -33,6 +33,7 @@ uses
 var
   // gtk-interface options
   UseTransientForModalWindows: boolean;
+  UpdatingTransientWindows: boolean;
 
 var
   //drag icons
@@ -287,6 +288,7 @@ implementation
 initialization
   ModalWindows:=nil;
   UseTransientForModalWindows:=true;
+  UpdatingTransientWindows:=false;
 
 end.