diff --git a/h5p.classes.php b/h5p.classes.php
index a65fc0d..d8ed62e 100644
--- a/h5p.classes.php
+++ b/h5p.classes.php
@@ -2510,10 +2510,8 @@ class H5PCore {
       'disabled' => $fetchingDisabled ? 1 : 0,
       'local_id' => hash('crc32', $this->fullPluginPath),
       'type' => $this->h5pF->getOption('site_type', 'local'),
-      'core_api_version' => json_encode(array(
-        'major' => H5PCore::$coreApi['majorVersion'],
-        'minor' => H5PCore::$coreApi['minorVersion']
-      ))
+      'core_api_version' => H5PCore::$coreApi['majorVersion'] . '.' .
+                            H5PCore::$coreApi['minorVersion']
     );
 
     // Register site if it is not registered