diff --git a/core/modules/rest/src/Plugin/views/display/RestExport.php b/core/modules/rest/src/Plugin/views/display/RestExport.php
index a0ef1e7..a9ed46c 100644
--- a/core/modules/rest/src/Plugin/views/display/RestExport.php
+++ b/core/modules/rest/src/Plugin/views/display/RestExport.php
@@ -107,7 +107,7 @@ public static function create(ContainerInterface $container, array $configuratio
    */
   public function initDisplay(ViewExecutable $view, array &$display, array &$options = NULL) {
     parent::initDisplay($view, $display, $options);
-    
+
     $request_content_type = $this->view->getRequest()->getRequestFormat();
     // Only use the requested content type if it's not 'html'. If it is then
     // default to 'json' to aid debugging.
diff --git a/core/modules/rest/src/Plugin/views/style/Serializer.php b/core/modules/rest/src/Plugin/views/style/Serializer.php
index 128a5e8..ba3ca6f 100644
--- a/core/modules/rest/src/Plugin/views/style/Serializer.php
+++ b/core/modules/rest/src/Plugin/views/style/Serializer.php
@@ -127,9 +127,12 @@ public function render() {
 
     // Get the content type configured in the display or fallback to the
     // default.
-    $default_content_type = empty($this->view->live_preview) ? $this->displayHandler->getContentType() : 'json';
-    $content_type = isset($this->options['formats'][$default_content_type]) ? $this->options['formats'][$default_content_type] : $default_content_type;
-
+    if ((empty($this->view->live_preview))) {
+      $content_type = $this->displayHandler->getContentType();
+    }
+    else {
+      $content_type = !empty($this->options['formats']) ? reset($this->options['formats']) : 'json';
+    }
     return $this->serializer->serialize($rows, $content_type);
   }