diff --git a/system/Config/Factories.php b/system/Config/Factories.php
index 2e24b5cef65c..ba49e9360a91 100644
--- a/system/Config/Factories.php
+++ b/system/Config/Factories.php
@@ -228,7 +228,7 @@ private static function setAlias(string $component, string $alias, string $class
         self::$updated[$component]         = true;
 
         // If a short classname is specified, also register FQCN to share the instance.
-        if (! isset(self::$aliases[$component][$class])) {
+        if (! isset(self::$aliases[$component][$class]) && ! self::isNamespaced($alias)) {
             self::$aliases[$component][$class] = $class;
         }
     }