diff --git a/documentation-tool.js b/documentation-tool.js
index f92b29f..7886aea 100644
--- a/documentation-tool.js
+++ b/documentation-tool.js
@@ -343,6 +343,10 @@ H5P.DocumentationTool = (function ($, NavigationMenu, JoubelUI, EventDispatcher)
   DocumentationTool.prototype.movePage = function (toPageIndex, skipFocus) {
     var self = this;
 
+    if (!toPageIndex) {
+      return;
+    }
+
     // Invalid value
     if ((toPageIndex + 1 > this.$pagesArray.length) || (toPageIndex < 0)) {
       return;
@@ -383,6 +387,9 @@ H5P.DocumentationTool = (function ($, NavigationMenu, JoubelUI, EventDispatcher)
 
     // Trigger xAPI event
     var progressedEvent = self.createXAPIEventTemplate('progressed');
+    if (progressedEvent.data.statement.object.definition.extensions === undefined) {
+      return;
+    }
     progressedEvent.data.statement.object.definition.extensions['http://id.tincanapi.com/extension/ending-point'] = toPageIndex;
     self.trigger(progressedEvent);
 
diff --git a/navigation-menu.js b/navigation-menu.js
index ee2d076..32b6ee9 100644
--- a/navigation-menu.js
+++ b/navigation-menu.js
@@ -92,6 +92,9 @@ H5P.DocumentationTool.NavigationMenu = (function ($, EventDispatcher) {
         self.$documentationToolContaner.removeClass('expanded');
         self.docTool.movePage(pageIndex, event);
         var progressedEvent = self.docTool.createXAPIEventTemplate('progressed'); // Using the parent documentation tool to create xapi template
+        if (progressedEvent.data.statement.object.definition.extensions === undefined) {
+          return;
+        }
         progressedEvent.data.statement.object.definition.extensions['http://id.tincanapi.com/extension/ending-point'] = pageIndex;
         self.trigger(progressedEvent);
       });