diff --git a/docs/src/pages/addons/writing-addons/index.md b/docs/src/pages/addons/writing-addons/index.md
index 2b80a6d96578..ca3e53367d62 100644
--- a/docs/src/pages/addons/writing-addons/index.md
+++ b/docs/src/pages/addons/writing-addons/index.md
@@ -65,6 +65,7 @@ import { STORY_CHANGED } from '@storybook/core-events';
 import addons, { types } from '@storybook/addons';
 
 const ADDON_ID = 'myaddon';
+const PARAM_KEY = 'myAddon';
 const PANEL_ID = `${ADDON_ID}/panel`;
 
 class MyPanel extends React.Component {