diff --git a/inc/footer.php b/inc/footer.php
index 2031ca3..f820bcb 100644
--- a/inc/footer.php
+++ b/inc/footer.php
@@ -1,4 +1,7 @@
-<?php $build = trim((string) @file_get_contents(__DIR__ . '/../build.txt')) ?: 'dev'; ?>
+<?php
+$build = trim((string) @file_get_contents(__DIR__ . '/../build.txt'));
+$build = preg_match('/[0-9a-f]{7,40}/i', $build, $m) ? $m[0] : ($build ?: 'dev');
+?>
 <?php require_once __DIR__ . '/buttons.php'; ?>
 </main>
 <footer>