diff --git a/src/Resize/Resizer.php b/src/Resize/Resizer.php
index e316af92c..3c39fbf62 100644
--- a/src/Resize/Resizer.php
+++ b/src/Resize/Resizer.php
@@ -110,6 +110,10 @@ public static function open($file): Resizer
      */
     protected function retainImageTransparency($img)
     {
+        if (!$img) {
+            return;
+        }
+
         if ($this->mime === 'image/gif') {
             $alphaColor = ['red' => 0, 'green' => 0, 'blue' => 0];
             $alphaIndex = imagecolortransparent($img);