diff --git a/lib.php b/lib.php
index 9800f1c997cf650850b3e6b9f4764f854acdfb37..1031060fa8ec18e59ef5df2a76f544b1472ee5ed 100644
--- a/lib.php
+++ b/lib.php
@@ -425,12 +425,12 @@ function pdfannotator_pluginfile($course, $cm, $context, $filearea, $args, $forc
     if ($filearea === 'post') {
         $commentid = 0;
         foreach ($args as $param) {
-            if ($DB->record_exists('pdfannotator_comments', ['id' => $param])) {
+            if (is_int($param) && $DB->record_exists('pdfannotator_comments', ['id' => $param])) {
                 $commentid = $param;
                 break;
             }
         }
-           
+
         $fullpath = rtrim("/$context->id/mod_pdfannotator/$filearea/$commentid/$relativepath", '/');
         if (!$file = $fs->get_file_by_hash(sha1($fullpath)) or $file->is_directory()) {
             //Annotations from other documents might have another contextid.