diff --git a/plone/app/discussion/browser/captcha.py b/plone/app/discussion/browser/captcha.py
new file mode 100644
index 0000000..787df43
--- /dev/null
+++ b/plone/app/discussion/browser/captcha.py
@@ -0,0 +1,44 @@
+from persistent import Persistent
+
+from z3c.form.field import Fields
+
+from zope import interface, schema
+
+from zope.annotation import factory
+from zope.annotation.attribute import AttributeAnnotations
+
+from zope.component import adapts, provideAdapter
+
+from zope.publisher.interfaces.browser import IDefaultBrowserLayer
+
+from zope.interface import Interface, implements
+
+from plone.z3cform.fieldsets import extensible
+from plone.z3cform.fieldsets.interfaces import IFormExtender
+
+from plone.app.discussion.comment import Comment
+
+class ICaptcha(Interface):
+    captcha = schema.TextLine(title=u"Type the word 'human' in all capital letters.",
+                              required=False)
+
+class Captcha(Persistent):
+    interface.implements(ICaptcha)
+    adapts(Comment)
+    captcha = u""
+
+Captcha = factory(Captcha)
+provideAdapter(Captcha)
+provideAdapter(AttributeAnnotations)
+
+class CaptchaExtender(extensible.FormExtender):
+    adapts(Interface, IDefaultBrowserLayer, Interface) # context, request, form
+
+    def __init__(self, context, request, form):
+        self.context = context
+        self.request = request
+        self.form = form
+
+    def update(self):
+        # Add all fields from the captcha interface
+        self.add(ICaptcha, prefix="extra")
\ No newline at end of file
diff --git a/plone/app/discussion/browser/configure.zcml b/plone/app/discussion/browser/configure.zcml
index 19f4589..0d35e35 100644
--- a/plone/app/discussion/browser/configure.zcml
+++ b/plone/app/discussion/browser/configure.zcml
@@ -64,6 +64,14 @@
         permission="zope2.View"
         />
 
+    <!-- Comment form extender -->
+    <adapter
+        factory=".captcha.Captcha" />
+
+    <adapter
+        factory=".captcha.CaptchaExtender"
+        provides="plone.z3cform.fieldsets.interfaces.IFormExtender" />
+
     <!-- Comment view -->
     <browser:view
         name="view"