diff --git a/post.php b/post.php
index b5852edb..5483600d 100644
--- a/post.php
+++ b/post.php
@@ -1402,7 +1402,7 @@ function handle_post(Context $ctx)
                     $file['thumbwidth'] = $size[0];
                     $file['thumbheight'] = $size[1];
                 } elseif (
-                    (($config['strip_exif'] && $file['exif_stripped']) || !$config['strip_exif']) &&
+                    (($config['strip_exif'] && isset($file['exif_stripped']) && $file['exif_stripped']) || !$config['strip_exif']) &&
                     $image->size->width <= $config['thumb_width'] &&
                     $image->size->height <= $config['thumb_height'] &&
                     $file['extension'] == ($config['thumb_ext'] ? $config['thumb_ext'] : $file['extension'])