diff --git a/fillpdf.module b/fillpdf.module
index 43108d6..8dd27de 100644
--- a/fillpdf.module
+++ b/fillpdf.module
@@ -220,9 +220,9 @@ function fillpdf_merge_pdf($fid, $nids = null, $webform_arr = null, $sample = nu
   	}
     
     foreach($webform_arr as $webform){
-      if(!$webform['sid']){ // user didn't specify submission-id, meaning they want most recent
+      if (empty($webform['sid'])) { // User did not specify submission ID, meaning they want most recent.
         $webform['sid'] = db_result(db_query('select sid from {webform_submissions} 
-          where nid=%d and uid=%d order by submitted desc', $webform['nid'], $user->uid));
+          WHERE nid = :nid AND uid = :uid ORDER BY submitted DESC', array(':nid' => (int) $webform['nid'], ':uid' => (int) $user->uid)));
       }
       $webforms[] = array( 
         'webform' => node_load($webform['nid']),