--- a/python/mach_commands.py
+++ b/python/mach_commands.py
@@ -61,20 +61,16 @@ class MachCommands(MachCommandBase):
                                 append_env=append_env)
 
     @Command('python-test', category='testing',
              description='Run Python unit tests with an appropriate test runner.')
     @CommandArgument('-v', '--verbose',
                      default=False,
                      action='store_true',
                      help='Verbose output.')
-    @CommandArgument('--stop',
-                     default=False,
-                     action='store_true',
-                     help='Stop running tests after the first error or failure.')
     @CommandArgument('-j', '--jobs',
                      default=1,
                      type=int,
                      help='Number of concurrent jobs to run. Default is 1.')
     @CommandArgument('--subsuite',
                      default=None,
                      help=('Python subsuite to run. If not specified, all subsuites are run. '
                            'Use the string `default` to only run tests without a subsuite.'))
@@ -90,17 +86,16 @@ class MachCommands(MachCommandBase):
             import mozfile
             mozfile.remove(tempdir)
 
     def run_python_tests(self,
                          tests=[],
                          test_objects=None,
                          subsuite=None,
                          verbose=False,
-                         stop=False,
                          jobs=1,
                          **kwargs):
         self._activate_virtualenv()
 
         # Python's unittest, and in particular discover, has problems with
         # clashing namespaces when importing multiple test modules. What follows
         # is a simple way to keep environments separate, at the price of
         # launching Python multiple times. Most tests are run via mozunit,