diff --git a/testing/xpcshell/runxpcshelltests.py b/testing/xpcshell/runxpcshelltests.py
index 2ea24738fd74..b54575893d90 100644
--- a/testing/xpcshell/runxpcshelltests.py
+++ b/testing/xpcshell/runxpcshelltests.py
@@ -463,10 +463,14 @@ class XPCShellTests(object):
         failure.setAttribute("type", str(result["failure"]["type"]))
         failure.setAttribute("message", result["failure"]["message"])
 
-        # Lossy translation but required to not break CDATA.
+        # Lossy translation but required to not break CDATA. Also, text could
+        # be None and Python 2.5's minidom doesn't accept None. Later versions
+        # do, however.
         cdata = result["failure"]["text"]
-        if cdata is not None:
-            cdata = cdata.replace("]]>", "]] >")
+        if not isinstance(cdata, str):
+            cdata = ""
+
+        cdata = cdata.replace("]]>", "]] >")
         text = doc.createCDATASection(cdata)
         failure.appendChild(text)
         testcase.appendChild(failure)