diff --git a/mercurial/hgweb/server.py b/mercurial/hgweb/server.py
--- a/mercurial/hgweb/server.py
+++ b/mercurial/hgweb/server.py
@@ -81,6 +81,7 @@ class _httprequesthandler(BaseHTTPServer
         except Exception:
             self._start_response("500 Internal Server Error", [])
             self._write("Internal Server Error")
+            self._done()
             tb = "".join(traceback.format_exception(*sys.exc_info()))
             self.log_error("Exception happened during processing "
                            "request '%s':\n%s", self.path, tb)
diff --git a/tests/get-with-headers.py b/tests/get-with-headers.py
--- a/tests/get-with-headers.py
+++ b/tests/get-with-headers.py
@@ -43,9 +43,8 @@ def request(host, path, show):
             print "%s: %s" % (h, response.getheader(h))
     if not headeronly:
         print
-        if response.status != 500:
-            data = response.read()
-            sys.stdout.write(data)
+        data = response.read()
+        sys.stdout.write(data)
 
         if twice and response.getheader('ETag', None):
             tag = response.getheader('ETag')
diff --git a/tests/hgweberror.py b/tests/hgweberror.py
new file mode 100644
--- /dev/null
+++ b/tests/hgweberror.py
@@ -0,0 +1,17 @@
+# A dummy extension that installs an hgweb command that throws an Exception.
+
+from mercurial.hgweb import webcommands
+
+def raiseerror(web, req, tmpl):
+    '''Dummy web command that raises an uncaught Exception.'''
+
+    # Simulate an error after partial response.
+    if 'partialresponse' in req.form:
+        req.respond(200, 'text/plain')
+        req.write('partial content\n')
+
+    raise AttributeError('I am an uncaught error!')
+
+def extsetup(ui):
+    setattr(webcommands, 'raiseerror', raiseerror)
+    webcommands.__all__.append('raiseerror')
diff --git a/tests/test-hgweb.t b/tests/test-hgweb.t
--- a/tests/test-hgweb.t
+++ b/tests/test-hgweb.t
@@ -579,4 +579,30 @@ errors
 
   $ cat errors.log
 
+Uncaught exceptions result in a logged error and canned HTTP response
+
+  $ "$TESTDIR/killdaemons.py" $DAEMON_PIDS
+  $ hg --config extensions.hgweberror=$TESTDIR/hgweberror.py serve -p $HGPORT -d --pid-file=hg.pid -A access.log -E errors.log
+  $ cat hg.pid >> $DAEMON_PIDS
+
+  $ $TESTDIR/get-with-headers.py localhost:$HGPORT 'raiseerror' transfer-encoding content-type
+  500 Internal Server Error
+  transfer-encoding: chunked
+  
+  Internal Server Error (no-eol)
+  [1]
+
+  $ head -1 errors.log
+  .* Exception happened during processing request '/raiseerror': (re)
+
+Uncaught exception after partial content sent
+
+  $ $TESTDIR/get-with-headers.py localhost:$HGPORT 'raiseerror?partialresponse=1' transfer-encoding content-type
+  200 Script output follows
+  transfer-encoding: chunked
+  content-type: text/plain
+  
+  partial content
+  Internal Server Error (no-eol)
+
   $ cd ..