diff --git a/system/src/Grav/Common/Page/Medium/Medium.php b/system/src/Grav/Common/Page/Medium/Medium.php
index de7e93250..b47d97791 100644
--- a/system/src/Grav/Common/Page/Medium/Medium.php
+++ b/system/src/Grav/Common/Page/Medium/Medium.php
@@ -265,7 +265,7 @@ class Medium extends Data implements RenderableInterface
      */
     public function thumbnail($type = 'auto')
     {
-        if (!in_array($type, $this->thumbnailTypes))
+        if ($type !== 'auto' && !in_array($type, $this->thumbnailTypes))
             return $this;
 
         if ($this->thumbnailType !== $type) {
diff --git a/system/src/Grav/Common/Page/Medium/ThumbnailImageMedium.php b/system/src/Grav/Common/Page/Medium/ThumbnailImageMedium.php
index ff916b4f6..3f40200cb 100644
--- a/system/src/Grav/Common/Page/Medium/ThumbnailImageMedium.php
+++ b/system/src/Grav/Common/Page/Medium/ThumbnailImageMedium.php
@@ -64,6 +64,19 @@ class ThumbnailImageMedium extends ImageMedium
         return $this->bubble('display', [$mode], false);
     }
 
+    /**
+     * Switch thumbnail.
+     *
+     * @param string $type
+     *
+     * @return $this
+     */
+    public function thumbnail($type = 'auto')
+    {
+        $this->bubble('thumbnail', [$type], false);
+        return $this->bubble('getThumbnail', [], false);
+    }
+
     /**
      * Turn the current Medium into a Link
      *
@@ -100,7 +113,7 @@ class ThumbnailImageMedium extends ImageMedium
     protected function bubble($method, array $arguments = [], $testLinked = true)
     {
         if (!$testLinked || $this->linked) {
-            return call_user_func_array(array($this->parent, $method), $arguments);
+            return $this->parent ? call_user_func_array(array($this->parent, $method), $arguments) : $this;
         } else {
             return call_user_func_array(array($this, 'parent::' . $method), $arguments);
         }