diff --git a/ext/spl/spl_dllist.h b/ext/spl/spl_dllist.h
index 15713997eac..daaf55fb203 100644
--- a/ext/spl/spl_dllist.h
+++ b/ext/spl/spl_dllist.h
@@ -24,9 +24,9 @@
 #include "php.h"
 #include "php_spl.h"
 
-PHPAPI zend_class_entry *spl_ce_SplDoublyLinkedList;
-PHPAPI zend_class_entry *spl_ce_SplQueue;
-PHPAPI zend_class_entry *spl_ce_SplStack;
+extern PHPAPI zend_class_entry *spl_ce_SplDoublyLinkedList;
+extern PHPAPI zend_class_entry *spl_ce_SplQueue;
+extern PHPAPI zend_class_entry *spl_ce_SplStack;
 
 PHP_MINIT_FUNCTION(spl_dllist);