--- a/python/mozbuild/mozbuild/controller/building.py
+++ b/python/mozbuild/mozbuild/controller/building.py
@@ -1002,17 +1002,17 @@ class BuildDriver(MozbuildObject):
                 # backend (Tup), and otherwise be harmless.
                 if active_backend:
                     if backend_out_of_date(mozpath.join(self.topobjdir,
                                                         'backend.%sBackend' %
                                                         active_backend)):
                         print('Build configuration changed. Regenerating backend.')
                         args = [config.substs['PYTHON'],
                                 mozpath.join(self.topobjdir, 'config.status')]
-                        self.run_process(args, cwd=self.topobjdir)
+                        self.run_process(args, cwd=self.topobjdir, pass_thru=True)
                     backend_cls = get_backend_class(active_backend)(config)
                     return backend_cls.build(self, output, jobs, verbose, what)
                 return None
 
             monitor.start_resource_recording()
 
             config = None
             try: