diff --git a/CHANGES.txt b/CHANGES.txt
index a4c2a8f..30cc666 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -4,6 +4,10 @@ Changelog
 1.0b10 (unreleased)
 -------------------
 
+- Fixed "global name 'WrongCaptchaCode' is not defined" if norobots captcha,
+  but no other validation package is installed.
+  [naro]
+
 - Check if there is a 'pending' review state in the current workflow for 
   comments instead of just checking for the 'comment_review_workflow'. This 
   allows integrators to use a custom review workflow. This fixes 
diff --git a/plone/app/discussion/browser/validator.py b/plone/app/discussion/browser/validator.py
index 8a46bc7..8e38e6d 100644
--- a/plone/app/discussion/browser/validator.py
+++ b/plone/app/discussion/browser/validator.py
@@ -21,6 +21,11 @@ from plone.app.discussion.interfaces import ICaptcha
 from plone.app.discussion.interfaces import IDiscussionSettings
 from plone.app.discussion.interfaces import IDiscussionLayer
 
+try:
+    from collective.z3cform.norobots.validator import WrongNorobotsAnswer
+except ImportError:
+    pass
+
 try:
     from plone.formwidget.captcha.validator import WrongCaptchaCode
 except ImportError:
@@ -31,7 +36,6 @@ try:
 except ImportError:
     pass
 
-
 class CaptchaValidator(validator.SimpleFieldValidator):
     implements(IValidator)
     adapts(Interface, IDiscussionLayer, Interface, IField, Interface)
@@ -48,7 +52,10 @@ class CaptchaValidator(validator.SimpleFieldValidator):
             captcha = getMultiAdapter((aq_inner(self.context), self.request), 
                                       name=settings.captcha)
             if not captcha.verify(input=value):
-                raise WrongCaptchaCode
+                if settings.captcha == 'norobots':
+                    raise WrongNorobotsAnswer
+                else:
+                    raise WrongCaptchaCode
             else:
                 return True