diff --git a/lib/installer.php b/lib/installer.php
index 6292b18467..dd1485b526 100644
--- a/lib/installer.php
+++ b/lib/installer.php
@@ -114,7 +114,7 @@ abstract class Installer
             $pass = false;
         }
 
-        $reqs = array('gd', 'curl',
+        $reqs = array('gd', 'curl', 'json',
                       'xmlwriter', 'mbstring', 'xml', 'dom', 'simplexml');
 
         foreach ($reqs as $req) {