diff --git a/libraries/classes/Config.php b/libraries/classes/Config.php
index dc39e010b3..a292c06774 100644
--- a/libraries/classes/Config.php
+++ b/libraries/classes/Config.php
@@ -1199,7 +1199,7 @@ class Config
      */
     public function getThemeUniqueValue(): int
     {
-        return (
+        return (int) (
             $this->source_mtime +
             $this->default_source_mtime +
             $this->get('user_preferences_mtime') +