diff --git a/Lib/test/test_minidom.py b/Lib/test/test_minidom.py
index 97bca2c..f1f1378 100644
--- a/Lib/test/test_minidom.py
+++ b/Lib/test/test_minidom.py
@@ -1314,6 +1314,11 @@
             for i in range(len(n1.childNodes)):
                 stack.append((n1.childNodes[i], n2.childNodes[i]))
 
+    def testSerializeCommentNodeWithDoubleHyphen(self):
+        doc = create_doc_without_doctype()
+        doc.appendChild(doc.createComment("foo--bar"))
+        self.assertRaises(ValueError, doc.toxml)
+
 def test_main():
     run_unittest(MinidomTest)
 
diff --git a/Lib/xml/dom/minidom.py b/Lib/xml/dom/minidom.py
index ae96033..02e82d9 100644
--- a/Lib/xml/dom/minidom.py
+++ b/Lib/xml/dom/minidom.py
@@ -1128,6 +1128,8 @@
         self.data = self.nodeValue = data
 
     def writexml(self, writer, indent="", addindent="", newl=""):
+        if "--" in self.data:
+            raise ValueError("'--' is not allowed in a comment node")
         writer.write("%s<!--%s-->%s" % (indent, self.data, newl))