--- a/testing/mochitest/Makefile.in
+++ b/testing/mochitest/Makefile.in
@@ -94,16 +94,17 @@ include $(topsrcdir)/build/automation-bu
 		ipc.js \
 		browser-harness.xul \
 		redirect-a11y.html \
 		redirect.html \
 		redirect.js \
 		$(topsrcdir)/build/pgo/server-locations.txt \
 		$(topsrcdir)/netwerk/test/httpserver/httpd.js \
 		mozprefs.js \
+		pywebsocket_ignore_sigint.py \
 		$(NULL)	
 
 _PYWEBSOCKET_FILES = \
 		pywebsocket/standalone.py \
 		$(NULL)
 
 _MOD_PYWEBSOCKET_FILES = \
 		pywebsocket/mod_pywebsocket/__init__.py \

new file mode 100644
--- /dev/null
+++ b/testing/mochitest/pywebsocket_ignore_sigint.py
@@ -0,0 +1,53 @@
+#
+# ***** BEGIN LICENSE BLOCK *****
+# Version: MPL 1.1/GPL 2.0/LGPL 2.1
+#
+# The contents of this file are subject to the Mozilla Public License Version
+# 1.1 (the "License"); you may not use this file except in compliance with
+# the License. You may obtain a copy of the License at
+# http://www.mozilla.org/MPL/
+#
+# Software distributed under the License is distributed on an "AS IS" basis,
+# WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+# for the specific language governing rights and limitations under the
+# License.
+#
+# The Original Code is mozilla.org code.
+#
+# The Initial Developer of the Original Code is the Mozilla Foundation.
+#
+# Portions created by the Initial Developer are Copyright (C) 2010
+# the Initial Developer. All Rights Reserved.
+#
+# Contributor(s):
+#     Justin Lebar <justin.lebar@gmail.com>
+#
+# Alternatively, the contents of this file may be used under the terms of
+# either the GNU General Public License Version 2 or later (the "GPL"), or
+# the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+# in which case the provisions of the GPL or the LGPL are applicable instead
+# of those above. If you wish to allow use of your version of this file only
+# under the terms of either the GPL or the LGPL, and not to allow others to
+# use your version of this file under the terms of the MPL, indicate your
+# decision by deleting the provisions above and replace them with the notice
+# and other provisions required by the GPL or the LGPL. If you do not delete
+# the provisions above, a recipient may use your version of this file under
+# the terms of any one of the MPL, the GPL or the LGPL.
+#
+# ***** END LICENSE BLOCK *****
+#
+
+"""A wrapper around pywebsocket's standalone.py which causes it to ignore
+SIGINT.
+
+"""
+
+import signal
+import sys
+
+if __name__ == '__main__':
+    sys.path = ['pywebsocket'] + sys.path
+    import standalone
+
+    signal.signal(signal.SIGINT, signal.SIG_IGN)
+    standalone._main()

--- a/testing/mochitest/runtests.py
+++ b/testing/mochitest/runtests.py
@@ -351,23 +351,31 @@ class MochitestServer:
       if rtncode is None:
         self._process.terminate()
     except:
       self._process.kill()
 
 class WebSocketServer(object):
   "Class which encapsulates the mod_pywebsocket server"
 
-  def __init__(self, automation, options, scriptdir):
+  def __init__(self, automation, options, scriptdir, debuggerInfo=None):
     self.port = options.webSocketPort
     self._automation = automation
     self._scriptdir = scriptdir
+    self.debuggerInfo = debuggerInfo
 
   def start(self):
-    script = os.path.join(self._scriptdir, 'pywebsocket/standalone.py')
+    # If we're running tests under an interactive debugger, tell the server to
+    # ignore SIGINT so it doesn't capture a ctrl+c meant for the debugger.
+    if self.debuggerInfo and self.debuggerInfo['interactive']:
+        scriptPath = 'pywebsocket_ignore_sigint.py'
+    else:
+        scriptPath = 'pywebsocket/standalone.py'
+
+    script = os.path.join(self._scriptdir, scriptPath)
     cmd = [sys.executable, script, '-p', str(self.port), '-w', self._scriptdir, '-l', os.path.join(self._scriptdir, "websock.log"), '--log-level=debug']
 
     self._process = self._automation.Process(cmd)
     pid = self._process.pid
     if pid < 0:
       print "Error starting websocket server."
       sys.exit(2)
     self._automation.log.info("INFO | runtests.py | Websocket server pid: %d", pid)
@@ -415,22 +423,23 @@ class Mochitest(object):
     elif options.a11y:
       testURL = testHost + self.A11Y_PATH
       if options.testPath:
         self.urlOpts.append("testPath=" + encodeURIComponent(options.testPath))
     elif options.browserChrome:
       testURL = "about:blank"
     return testURL
 
-  def startWebSocketServer(self, options):
+  def startWebSocketServer(self, options, debuggerInfo):
     """ Launch the websocket server """
     if options.webServer != '127.0.0.1':
       return
 
-    self.wsserver = WebSocketServer(self.automation, options, self.SCRIPT_DIRECTORY)
+    self.wsserver = WebSocketServer(self.automation, options,
+                                    self.SCRIPT_DIRECTORY, debuggerInfo)
     self.wsserver.start()
 
   def stopWebSocketServer(self, options):
     if options.webServer != '127.0.0.1':
       return
 
     self.wsserver.stop()
 
@@ -592,17 +601,17 @@ class Mochitest(object):
     if browserEnv is None:
       return 1
 
     manifest = self.buildProfile(options)
     if manifest is None:
       return 1
 
     self.startWebServer(options)
-    self.startWebSocketServer(options)
+    self.startWebSocketServer(options, debuggerInfo)
 
     testURL = self.buildTestPath(options)
     self.buildURLOptions(options)
     if len(self.urlOpts) > 0:
       testURL += "?" + "&".join(self.urlOpts)
 
     # Remove the leak detection file so it can't "leak" to the tests run.
     # The file is not there if leak logging was not enabled in the application build.