diff --git a/Button/button_def.mch b/Button/button_def.mch
index 1f348a173125b81ce384d2a677c4491ee8223be2..8a7bacac5ad050f9049d7f16b70e60e9f19c6b81 100644
--- a/Button/button_def.mch
+++ b/Button/button_def.mch
@@ -8,12 +8,13 @@ DEFINITIONS
   VISB_SVG_UPDATES == rec(`id`:"button",
      fill: IF button=TRUE THEN "green" ELSE "red" END);
   VISB_SVG_HOVERS == rec(`id`:"button",
-     stroke:"gray", `stroke-width`:"5")
+     stroke:"gray", `stroke-width`:"5");
+  VISB_SVG_EVENTS == rec(`id`:"button", event:"toggle_button", predicate:"btrue");
 VARIABLES button
 INVARIANT button:BOOL
 INITIALISATION button := FALSE
 OPERATIONS
-  toggle_button = BEGIN
+  toggle_button /* desc change status of button */ = BEGIN
     button:= bool(button=FALSE)
   END
 END
\ No newline at end of file