diff -ru debug-old/wdg_validate.py debug-new/wdg_validate.py
--- debug-old/wdg_validate.py	2007-10-06 23:17:22.000000000 +0100
+++ debug-new/wdg_validate.py	2007-10-06 23:25:06.000000000 +0100
@@ -60,8 +60,8 @@
         page = output.getvalue()
         status, headers = response
         v = wsgilib.header_value(headers, 'content-type')
-        if (not v.startswith('text/html')
-            and not v.startswith('text/xhtml+xml')):
+        if (v is None or (not v.startswith('text/html')
+            and not v.startswith('text/xhtml+xml'))):
             # Can't validate
             # @@: Should validate CSS too... but using what?
             return [page]