diff --git a/app/code/core/Mage/Core/Model/Design/Config.php b/app/code/core/Mage/Core/Model/Design/Config.php
index 3ceba712e..d7c24d16e 100644
--- a/app/code/core/Mage/Core/Model/Design/Config.php
+++ b/app/code/core/Mage/Core/Model/Design/Config.php
@@ -43,8 +43,12 @@ public function __construct(array $params = [])
             $files = [];
 
             foreach (Maho::getInstalledPackages() as $package => $info) {
-                $path = $package === 'root' ? $this->_designRoot : $info['path'];
-                foreach (glob("$path/app/design/*/*/*/etc/theme.xml") as $file) {
+                if ($package === 'root') {
+                    $designRoot = $this->_designRoot;
+                } else {
+                    $designRoot = $info['path'] . '/app/design';
+                }
+                foreach (glob("$designRoot/*/*/*/etc/theme.xml") as $file) {
                     $files[Maho::toRelativePath($file)] = $file;
                 }
             }