diff --git a/rootdir/Android.mk b/rootdir/Android.mk
index d90f988..d53af2f 100644
--- a/rootdir/Android.mk
+++ b/rootdir/Android.mk
@@ -70,6 +70,11 @@
     ; mkdir -p $(dir $(TARGET_ROOT_OUT)/$(word 2,$(p))) \
     ; ln -sf $(word 1,$(p)) $(TARGET_ROOT_OUT)/$(word 2,$(p)))
 endif
+# The A/B updater uses a top-level /postinstall directory to mount the new
+# system before reboot.
+ifeq ($(AB_OTA_UPDATER),true)
+  LOCAL_POST_INSTALL_CMD += ; mkdir -p $(TARGET_ROOT_OUT)/postinstall
+endif
 
 include $(BUILD_SYSTEM)/base_rules.mk
 
diff --git a/rootdir/init.rc b/rootdir/init.rc
index b26e6fc..194b41b 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -23,6 +23,9 @@
     # Shouldn't be necessary, but sdcard won't start without it. http://b/22568628.
     mkdir /mnt 0775 root system
 
+    # Set the security context of /postinstall if present.
+    restorecon /postinstall
+
     start ueventd
 
 on init