diff --git a/src/ConfigHelper.php b/src/ConfigHelper.php
index aebab2f..be0af98 100644
--- a/src/ConfigHelper.php
+++ b/src/ConfigHelper.php
@@ -109,7 +109,7 @@ public static function get_extensions($className)
             foreach ($extensions as $extensionClass) {
                 // Ignore parameters (ie. "Versioned('Stage', 'Live')")
                 $extensionClass = explode('(', $extensionClass, 2);
-                $extensionClass = $extensionClass[0];
+                $extensionClass = Utility::getClassFromInjectorString($extensionClass[0])->getClassName();
 
                 $extensionClasses[$extensionClass] = $extensionClass;
             }