diff --git a/src/context.js b/src/context.js
index 9a34ea8..420c65f 100644
--- a/src/context.js
+++ b/src/context.js
@@ -32,6 +32,10 @@ class PageBuilder extends ScriptAndStyleContext {
      * @type {Array<CompelExtension>}
      */
     _extensions;
+    /**
+     * @type {Map<string,*>}
+     */
+    _groups;
 
     constructor() {
         super();