Index: nevow/test/test_appserver.py
===================================================================
--- nevow/test/test_appserver.py	(revision 18026)
+++ nevow/test/test_appserver.py	(working copy)
@@ -94,6 +94,7 @@
             lambda : self.fail(),
             asserterr)
 
+from twisted.internet import defer
 
 class TestSiteAndRequest(testutil.TestCase):
     def renderResource(self, resource, path):
@@ -130,6 +131,19 @@
         return self.renderResource(Res1(), 'bar').addCallback(
             lambda result: self.assertEquals(result, 'world'))
 
+    def test_connectionLost(self):
+        d = defer.Deferred()
+        class Res(Render):
+            def renderHTTP(self, ctx):
+                return d
+        s = appserver.NevowSite(Res())
+        r = appserver.NevowRequest(testutil.FakeChannel(s), True)
+        r.path = 'boo'
+        r.process()
+        r.connectionLost(Exception('Just Testing'))
+        d.callback('finished')
+
+
 from twisted.internet import protocol, address
 
 class FakeTransport(protocol.FileWrapper):
Index: nevow/appserver.py
===================================================================
--- nevow/appserver.py	(revision 18026)
+++ nevow/appserver.py	(working copy)
@@ -120,7 +120,13 @@
     def __init__(self, *args, **kw):
         server.Request.__init__(self, *args, **kw)
         tpc.Componentized.__init__(self)
+        self._lostConnection = False
 
+        def flagLostConnection(err):
+            self._lostConnection = True
+
+        self.notifyFinish().addErrback(flagLostConnection)
+
     def process(self):
         # extra request parsing
         if self.method == 'POST':
@@ -173,10 +179,13 @@
         self.deferred.callback("")
 
     def finishRequest( self, success ):
-        server.Request.finish(self)
+        if not self._lostConnection:
+            server.Request.finish(self)
 
     def _cbFinishRender(self, html, ctx):
-        if isinstance(html, str):
+        if self._lostConnection:
+            pass
+        elif isinstance(html, str):
             self.write(html)
             self.finishRequest(  True )
         elif html is errorMarker: