diff --git a/Lib/xml/dom/expatbuilder.py b/Lib/xml/dom/expatbuilder.py
index a2f8a33..4fba875 100644
--- a/Lib/xml/dom/expatbuilder.py
+++ b/Lib/xml/dom/expatbuilder.py
@@ -242,7 +242,7 @@
         doctype = self.document.implementation.createDocumentType(
             doctypeName, publicId, systemId)
         doctype.ownerDocument = self.document
-        self.document.childNodes.append(doctype)
+        _append_child(self.document, doctype)
         self.document.doctype = doctype
         if self._filter and self._filter.acceptNode(doctype) == FILTER_REJECT:
             self.document.doctype = None