--- a/testing/marionette/harness/marionette_harness/runtests.py
+++ b/testing/marionette/harness/marionette_harness/runtests.py
@@ -63,17 +63,20 @@ class MarionetteHarness(object):
     def process_args(self):
         if self.args.get('pydebugger'):
             self._testcase_class.pydebugger = __import__(self.args['pydebugger'])
 
     def run(self):
         self.process_args()
         tests = self.args.pop('tests')
         runner = self._runner_class(**self.args)
-        runner.run_tests(tests)
+        try:
+            runner.run_tests(tests)
+        finally:
+            runner.cleanup()
         return runner.failed + runner.crashed
 
 
 def cli(runner_class=MarionetteTestRunner, parser_class=MarionetteArguments,
         harness_class=MarionetteHarness, testcase_class=MarionetteTestCase, args=None):
     """
     Call the harness to parse args and run tests.