--- a/dom/media/test/external/mach_commands.py
+++ b/dom/media/test/external/mach_commands.py
@@ -14,33 +14,35 @@ from mozbuild.base import (
 
 from mach.decorators import (
     CommandProvider,
     Command,
 )
 
 def setup_argument_parser():
     from external_media_harness.runtests import MediaTestArguments
-    return MediaTestArguments()
+    from mozlog.structured import commandline
+    parser = MediaTestArguments()
+    commandline.add_logging_group(parser)
+    return parser
 
 
 def run_external_media_test(tests, testtype=None, topsrcdir=None, **kwargs):
     from external_media_harness.runtests import (
         FirefoxMediaHarness,
         MediaTestArguments,
         MediaTestRunner,
         mn_cli,
     )
 
     from mozlog.structured import commandline
 
     from argparse import Namespace
 
-    parser = MediaTestArguments()
-    commandline.add_logging_group(parser)
+    parser = setup_argument_parser()
 
     if not tests:
         tests = [os.path.join(topsrcdir,
                  'dom/media/test/external/external_media_tests/manifest.ini')]
 
     args = Namespace(tests=tests)
 
     for k, v in kwargs.iteritems():

--- a/testing/firefox-ui/mach_commands.py
+++ b/testing/firefox-ui/mach_commands.py
@@ -15,22 +15,28 @@ from mozbuild.base import (
 from mach.decorators import (
     Command,
     CommandProvider,
 )
 
 
 def setup_argument_parser_functional():
     from firefox_ui_harness.arguments.base import FirefoxUIArguments
-    return FirefoxUIArguments()
+    from mozlog.structured import commandline
+    parser = FirefoxUIArguments()
+    commandline.add_logging_group(parser)
+    return parser
 
 
 def setup_argument_parser_update():
     from firefox_ui_harness.arguments.update import UpdateArguments
-    return UpdateArguments()
+    from mozlog.structured import commandline
+    parser = UpdateArguments()
+    commandline.add_logging_group(parser)
+    return parser
 
 
 def run_firefox_ui_test(testtype=None, topsrcdir=None, **kwargs):
     from mozlog.structured import commandline
     from argparse import Namespace
     import firefox_ui_harness
 
     if testtype == 'functional':