diff --git a/lcl/interfaces/win32/win32wsdialogs.pp b/lcl/interfaces/win32/win32wsdialogs.pp
index 89eb0ab369..4034a34756 100644
--- a/lcl/interfaces/win32/win32wsdialogs.pp
+++ b/lcl/interfaces/win32/win32wsdialogs.pp
@@ -1073,6 +1073,7 @@ var
   Dialog: IFileDialog;
   Idx: Integer;
 begin
+  Idx := -1;
   if (ACommonDialog.Handle <> 0) and (ACommonDialog.Handle <> INVALID_HANDLE_VALUE) then
   begin
     if CanUseVistaDialogs(TOpenDialog(ACommonDialog)) and not IsXPStyleFallBack(TOpenDialog(ACommonDialog), Idx) then