diff -r dfe62f685538 Lib/xml/dom/minidom.py
--- a/Lib/xml/dom/minidom.py	Wed May 27 22:00:46 2015 -0700
+++ b/Lib/xml/dom/minidom.py	Thu May 28 11:00:43 2015 +0300
@@ -302,6 +302,10 @@
 def _write_data(writer, data):
     "Writes datachars to writer."
     if data:
+        if not isinstance(data, str):
+            raise TypeError("data must be str, received %s" % \
+                type(data).__name__)
+        
         data = data.replace("&", "&amp;").replace("<", "&lt;"). \
                     replace("\"", "&quot;").replace(">", "&gt;")
         writer.write(data)