diff --git a/ykval-sync.php b/ykval-sync.php
index 7f81983..12c81af 100644
--- a/ykval-sync.php
+++ b/ykval-sync.php
@@ -7,6 +7,11 @@ $apiKey = '';
 
 header("content-type: text/plain");
 
+if(empty($_SERVER['QUERY_STRING'])) {
+  sendResp(S_MISSING_PARAMETER, $apiKey);
+  exit;
+}
+
 $myLog = new Log('ykval-sync');
 $myLog->addField('ip', $_SERVER['REMOTE_ADDR']);