diff --git a/client.mk b/client.mk
index 951f3a1670575..27556a4564890 100644
--- a/client.mk
+++ b/client.mk
@@ -432,15 +432,6 @@ endif # MOZ_CURRENT_PROJECT
 ####################################
 # Postflight, after building all projects
 
-ifdef MOZ_AUTOMATION
-ifndef MOZ_CURRENT_PROJECT
-realbuild::
-# Only run the automation/build target for the first project.
-# (i.e. first platform of universal builds)
-	$(MAKE) -f $(TOPSRCDIR)/client.mk automation/build $(addprefix MOZ_CURRENT_PROJECT=,$(firstword $(MOZ_BUILD_PROJECTS)))
-endif
-endif
-
 realbuild postflight_all::
 ifeq (,$(MOZ_CURRENT_PROJECT)$(if $(MOZ_POSTFLIGHT_ALL),,1))
 # Don't run postflight_all for individual projects in multi-project builds
diff --git a/python/mozbuild/mozbuild/mach_commands.py b/python/mozbuild/mozbuild/mach_commands.py
index d30e370de7f0d..a2cb8db61945d 100644
--- a/python/mozbuild/mozbuild/mach_commands.py
+++ b/python/mozbuild/mozbuild/mach_commands.py
@@ -434,6 +434,27 @@ def build(self, what=None, disable_extra_make_dependencies=None, jobs=0,
                     allow_parallel=False, ensure_exit_code=False, num_jobs=jobs,
                     silent=not verbose)
 
+                make_extra = self.mozconfig['make_extra'] or []
+                make_extra = dict(m.split('=', 1) for m in make_extra)
+
+                # For universal builds, we need to run the automation steps in
+                # the first architecture from MOZ_BUILD_PROJECTS
+                projects = make_extra.get('MOZ_BUILD_PROJECTS')
+                append_env = None
+                if projects:
+                    project = projects.split()[0]
+                    append_env = {b'MOZ_CURRENT_PROJECT': project.encode('utf-8')}
+                    subdir = os.path.join(self.topobjdir, project)
+                else:
+                    subdir = self.topobjdir
+                moz_automation = os.getenv('MOZ_AUTOMATION') or make_extra.get('export MOZ_AUTOMATION', None)
+                if moz_automation and status == 0:
+                    status = self._run_make(target='automation/build', directory=subdir,
+                        line_handler=output.on_line, log=False, print_directory=False,
+                        ensure_exit_code=False, num_jobs=jobs, silent=not verbose,
+                        append_env=append_env
+                    )
+
                 self.log(logging.WARNING, 'warning_summary',
                     {'count': len(monitor.warnings_database)},
                     '{count} compiler warnings present.')