diff --git a/lcl/interfaces/gtk2/gtk2wsstdctrls.pp b/lcl/interfaces/gtk2/gtk2wsstdctrls.pp
index a40cae9754..c3da31df13 100644
--- a/lcl/interfaces/gtk2/gtk2wsstdctrls.pp
+++ b/lcl/interfaces/gtk2/gtk2wsstdctrls.pp
@@ -1564,7 +1564,7 @@ begin
      (csDesigning in AWinControl.ComponentState) then
     Exit;
   Value.g_type := G_TYPE_BOOLEAN;
-  Value.data[0].v_int := gTRUE;
+  Value.data[0].v_int := longint(gTRUE);
 
   g_object_set_property(PGObject(AWidget), 'button-sensitivity', @Value);
 end;