diff --git a/exp_gui/module/prototype.lua b/exp_gui/module/prototype.lua
index 66a1b28e..ea1e6a31 100644
--- a/exp_gui/module/prototype.lua
+++ b/exp_gui/module/prototype.lua
@@ -274,6 +274,7 @@ function ExpElement._prototype:draw(definition)
 
     if not next(signals) then
         -- If no signals then skip var arg
+        --- @cast definition LuaGuiElement.add_param
         self._draw = function(_, parent)
             return parent.add(definition)
         end