diff --git a/post.php b/post.php
index fc2a2583..41e93165 100644
--- a/post.php
+++ b/post.php
@@ -1112,7 +1112,7 @@ function handle_post(){
             if (($file['extension'] == "pdf" && $config['pdf_file_thumbnail']) || 
                 ($file['extension'] == "djvu" && $config['djvu_file_thumbnail']) ){
                 $path = $file['thumb'];
-                $error = shell_exec_error( 'convert -thumbnail x300 -background white -alpha remove ' .
+                $error = shell_exec_error( 'convert -size '.$config['thumb_width'].'x'.$config['thumb_height'].' -thumbnail '.$config['thumb_width'].'x'.$config['thumb_height'].' -background white -alpha remove ' .
                 escapeshellarg($file['tmp_name']. '[0]') . ' ' .
                 escapeshellarg($file['thumb']));