diff --git a/h5p.classes.php b/h5p.classes.php
index d9b4e4b..df958b0 100644
--- a/h5p.classes.php
+++ b/h5p.classes.php
@@ -1806,7 +1806,7 @@ class H5PCore {
 
   public static $coreApi = array(
     'majorVersion' => 1,
-    'minorVersion' => 16
+    'minorVersion' => 19
   );
   public static $styles = array(
     'styles/h5p.css',
diff --git a/js/h5p-content-upgrade-process.js b/js/h5p-content-upgrade-process.js
index 81e55de..5277eb6 100644
--- a/js/h5p-content-upgrade-process.js
+++ b/js/h5p-content-upgrade-process.js
@@ -26,7 +26,7 @@ H5P.ContentUpgradeProcess = (function (Version) {
 
     // Make extras possible to work with
     for (var element in extras) {
-      if (extras.hasOwnProperty(element)) {
+      if (extras[element] !== undefined) {
         try {
           extras[element] = JSON.parse(extras[element]);
           if (!(extras[element] instanceof Object)) {
diff --git a/js/h5p-content-upgrade.js b/js/h5p-content-upgrade.js
index 564a0a8..de17fc1 100644
--- a/js/h5p-content-upgrade.js
+++ b/js/h5p-content-upgrade.js
@@ -248,10 +248,9 @@
     self.current++;
     self.working++;
 
-    // Rewrap metadata
-    if (self.extras.metadata) {
-      self.extras.metadata = self.extras.metadata[id];
-    }
+    var extras = {
+      metadata: (self.extras.metadata && self.extras.metadata[id]) ? self.extras.metadata[id] : undefined
+    };
 
     if (worker) {
       worker.postMessage({
@@ -261,11 +260,11 @@
         oldVersion: info.library.version,
         newVersion: self.version.toString(),
         params: self.parameters[id],
-        extras: self.extras
+        extras: extras
       });
     }
     else {
-      new H5P.ContentUpgradeProcess(info.library.name, new Version(info.library.version), self.version, self.parameters[id], self.extras, id, function loadLibrary(name, version, next) {
+      new H5P.ContentUpgradeProcess(info.library.name, new Version(info.library.version), self.version, self.parameters[id], extras, id, function loadLibrary(name, version, next) {
         self.loadLibrary(name, version, function (err, library) {
           if (library.upgradesScript) {
             self.loadScript(library.upgradesScript, function (err) {