diff --git a/ext/domxml/php_domxml.c b/ext/domxml/php_domxml.c
index 7b2fed2dc70..2bb2c842bca 100644
--- a/ext/domxml/php_domxml.c
+++ b/ext/domxml/php_domxml.c
@@ -165,7 +165,9 @@ PHP_MINIT_FUNCTION(domxml)
 	REGISTER_LONG_CONSTANT("XML_DOCUMENT_TYPE_NODE", XML_DOCUMENT_TYPE_NODE, CONST_CS | CONST_PERSISTENT);
 	REGISTER_LONG_CONSTANT("XML_DOCUMENT_FRAG_NODE", XML_DOCUMENT_FRAG_NODE, CONST_CS | CONST_PERSISTENT);
 	REGISTER_LONG_CONSTANT("XML_NOTATION_NODE", XML_NOTATION_NODE, CONST_CS | CONST_PERSISTENT);
+#ifdef XML_GLOBAL_NAMESPACE
 	REGISTER_LONG_CONSTANT("XML_GLOBAL_NAMESPACE", XML_GLOBAL_NAMESPACE, CONST_CS | CONST_PERSISTENT);
+#endif
 	REGISTER_LONG_CONSTANT("XML_LOCAL_NAMESPACE", XML_LOCAL_NAMESPACE, CONST_CS | CONST_PERSISTENT);
 	return SUCCESS;
 }