diff --git a/lcl/extdlgs.pas b/lcl/extdlgs.pas
index 30ba045a01..8fb85612a3 100644
--- a/lcl/extdlgs.pas
+++ b/lcl/extdlgs.pas
@@ -42,8 +42,9 @@ type
     FPreviewFileDialog: TPreviewFileDialog;
   protected
     class procedure WSRegisterClass; override;
-    procedure SetPreviewFileDialog(const AValue: TPreviewFileDialog);
     class function GetControlClassDefaultSize: TSize; override;
+    procedure SetPreviewFileDialog(const AValue: TPreviewFileDialog);
+    procedure CreateParams(var Params: TCreateParams); override;
   public
     constructor Create(TheOwner: TComponent); override;
     property PreviewFileDialog: TPreviewFileDialog read FPreviewFileDialog
@@ -258,6 +259,13 @@ begin
   FPreviewFileDialog:=AValue;
 end;
 
+procedure TPreviewFileControl.CreateParams(var Params: TCreateParams);
+begin
+  inherited CreateParams(Params);
+  if Params.WndParent = 0 then
+    Params.Style := Params.Style and not WS_CHILD;
+end;
+
 class function TPreviewFileControl.GetControlClassDefaultSize: TSize;
 begin
   Result.CX := 200;