diff --git a/backend.php b/backend.php
index 8b3a3e061..c322e1e55 100644
--- a/backend.php
+++ b/backend.php
@@ -30,7 +30,7 @@
 	$op = (string)clean($op);
 	$method = (string)clean($method);
 
-	$scope = Tracer::start(__FILE__, ['tags' => $_REQUEST]);
+	$scope = Tracer::start(__FILE__, ['tags' => json_encode($_REQUEST)]);
 
 	startup_gettext();