diff --git a/php/src/Google/Protobuf/Internal/Descriptor.php b/php/src/Google/Protobuf/Internal/Descriptor.php
index d0d1e2599f..f8d24e450a 100644
--- a/php/src/Google/Protobuf/Internal/Descriptor.php
+++ b/php/src/Google/Protobuf/Internal/Descriptor.php
@@ -129,7 +129,7 @@ class Descriptor
         $message_name_without_package  = "";
         $classname = "";
         $fullname = "";
-        getFullClassName(
+        GPBUtil::getFullClassName(
             $proto,
             $containing,
             $file_proto,