--- a/tools/lint/mach_commands.py
+++ b/tools/lint/mach_commands.py
@@ -32,16 +32,17 @@ class MachCommands(MachCommandBase):
 
     @Command(
         'lint', category='devenv',
         description='Run linters.',
         parser=setup_argument_parser)
     def lint(self, *runargs, **lintargs):
         """Run linters."""
         from mozlint import cli
+        lintargs.setdefault('root', self.topsrcdir)
         lintargs['exclude'] = ['obj*']
         cli.SEARCH_PATHS.append(here)
         self._activate_virtualenv()
         return cli.run(*runargs, **lintargs)
 
     @Command('eslint', category='devenv',
              description='Run eslint or help configure eslint for optimal development.')
     @CommandArgument('paths', default=None, nargs='*',