diff --git a/Routing/RestRouteCollection.php b/Routing/RestRouteCollection.php
index a4745bcb9..734de23a6 100644
--- a/Routing/RestRouteCollection.php
+++ b/Routing/RestRouteCollection.php
@@ -62,7 +62,10 @@ public function prependRouteControllersWithPrefix($prefix)
     public function setDefaultFormat($format)
     {
         foreach (parent::all() as $route) {
-            $route->setDefault('_format', $format);
+            // Set default format only if not set already (could be defined in annotation)
+            if (!$route->getDefault('_format')) {
+                $route->setDefault('_format', $format);
+            }
         }
     }